ABS light and break light on with Random jerking while driving and periodic stalls

[pcharm129]

Ok. So I've been having this issue for some time now. Randomly, I experience a problem where I'm driving and the truck will jerk (as if you are stomping and releasing the gas pedal), and the ABS and brake lights will come on together at the same time. It usually happens when taking off from a standstill, like at a red light. Or when I'm moving slowly, then need to accelerate quickly. Usually, the issue disappears once the truck hits around 30 or 40mph. The vehicle also stalls or tries to stall periodically, and the idle used to be a bit smoother. I've been told by a couple mechanics that it's probably the Throttle Position Sensor. But since the TBS is part of the Throttle Body, I'd like to be pretty sure that it's the likely culprit before spending $200+ on a new one. Can anyone help me out with this situation???

 

[CaptainXL]

I've been told by a couple mechanics that it's probably the Throttle Position Sensor.

First order of business would be to have the codes retrieved. The list of symptoms is just too broad to make an informed decision at this time. Bring it over to one of your mechanics and have them scan for codes or do it yourself. Let us know what codes come up.

 

[The_Roadie]

And please fill out your profile so we know what year and engine you're working with. And how many miles and any other maintenance history.

In my experience, TPS problems will always throw a code and light up the Check Engine Light. Do you have the CEL on?

They also very often light up the REP (reduced engine power) light and you get to limp home.

ABS and brake lights on together are very often a loose or flaky ground, either on the frame rail near the ABS control module, or at the bottom of the radio stack on the passenger side of the transmission hump.

Erratic idle on an I6 is a classic dirty throttle body. Needs to be removed and cleaned every 30-40K miles.

 

[pcharm129]

Well, oddly enough, there's no codes being thrown. I've had it checked numerous times since the start of this issue. I'm kind of a serial tester. I test with or without a check engine light. And Roadie, I have definitely experienced an REP light during several of the occurences. I had a PCM tune this summer via PCMForLess. I had a code (can't recall the #) that stated I had a bad PCM, the wrong PCM, or that it needed reprogramming. So, since I wanted a tune anyway I went ahead and did that. It did resolve the related code, but did nothing for the situation at hand. Oh, and I've already cleaned the Throttle Body twice in the last 18 months.

 

[CaptainXL]

Whats your mileage and maint history.

 

[pcharm129]

There's about 130,000 miles on her. I bought her at about 118,000 in Oct 2010. I've done a few oil and spark plug changes. This summer I had to replace 2 coil packs. Ummmmm, added a Mechman alternator plus big 3 upgrade, Spectre CAI, removed resonator, changed fan clutch, motor mounts, rotors, brake pads. That's pretty much it.

 

[CaptainXL]

There's about 130,000 miles on her. I bought her at about 118,000 in Oct 2010. I've done a few oil and spark plug changes. This summer I had to replace 2 coil packs. Ummmmm, added a Mechman alternator plus big 3 upgrade, Spectre CAI, removed resonator, changed fan clutch, motor mounts, rotors, brake pads. That's pretty much it.

No fuel filter or fuel pressure regulator? What plugs did you use?

 

[Wooluf1952]

There's about 130,000 miles on her. I bought her at about 118,000 in Oct 2010. I've done a few oil and spark plug changes. This summer I had to replace 2 coil packs. Ummmmm, added a Mechman alternator plus big 3 upgrade, Spectre CAI, removed resonator, changed fan clutch, motor mounts, rotors, brake pads. That's pretty much it.

I may be miss-reading, but plugs ( AC Delco Iridium 41-103 are strongly recommended) only need to be replaced every 100k miles.

 

[pcharm129]

No. I haven't replaced the fuel filter or fuel pressure regulator. And the plugs were the ACDelco Iridiums. And I replaced a plug or 2 more than once when I changed the coil packs for misfiring issues. Once, cylinder 6 had flooded with water so definitely had to change plug (heavy rain storm). Now that I'm thinking, I believe I actually changed 3 coil packs.

 

[CaptainXL]

No. I haven't replaced the fuel filter or fuel pressure regulator. And the plugs were the ACDelco Iridiums. And I replaced a plug or 2 more than once when I changed the coil packs for misfiring issues. Once, cylinder 6 had flooded with water so definitely had to change plug (heavy rain storm). Now that I'm thinking, I believe I actually changed 3 coil packs.

Did you get any water in the fuel tank from Sandy?

 

[pcharm129]

No. But this is not a new problem. It's been going on for over a year now.

 

[CaptainXL]

No. But this is not a new problem. It's been going on for over a year now.

And the fuel filter has never been changed? Check fuel pressure. Clean injectors.

On this ignition side check for misfires. Sounds like you might have most of the coils damaged. Do the AIP seal fix. Do you have a subscription to Alldatadiy? Look at the tsb's there and perform the seal fix.

 

[pcharm129]

Ok. I'll check out Alldatadiy. And I'll see about gettin the injectors cleaned. Thanks for your input! I appreciate it.

 

[pcharm129]

Hey. Just as an update, I checked the fuel pressure and it was normal. I believe 57. I went ahead and changed the fuel filter anyway, since it hadn't been changed in, at least, the last 27 months. She stalled on me yesterday when I stopped for a light. And It's not throwing any codes. I just bought one of those bluetooth OBD2 interfaces from ebay. It's pretty cool. Just got it today. Have only used it with the Torque app for android so far. It doesn't seem to be reading a lot of sensors that I think it should, but maybe it's simply because I'm using the free Lite version. Or maybe the Trailblazer ECU doesn't broadcast certain info via ODB2 (like voltage, fuel level, and fuel pressure). I have several PC based programs to try, but haven't gotten around to it yet. As for the physical labor, anything may have to wait until it gets warmer since I don't have a garage or a driveway to work on it. But, if you guys can think of any other suggestions, I'd really appreciate hearing them. I just may try to squeeze in a new throttle body if I can, before the weather gets too bad. But I would HATE to have to spend all that money on a new one, just to find out that that's not the problem...

 

[BRomanJr]

Hey. Just as an update, I checked the fuel pressure and it was normal. I believe 57. I went ahead and changed the fuel filter anyway, since it hadn't been changed in, at least, the last 27 months. She stalled on me yesterday when I stopped for a light. And It's not throwing any codes. I just bought one of those bluetooth OBD2 interfaces from ebay. It's pretty cool. Just got it today. Have only used it with the Torque app for android so far. It doesn't seem to be reading a lot of sensors that I think it should, but maybe it's simply because I'm using the free Lite version. Or maybe the Trailblazer ECU doesn't broadcast certain info via ODB2 (like voltage, fuel level, and fuel pressure). I have several PC based programs to try, but haven't gotten around to it yet. As for the physical labor, anything may have to wait until it gets warmer since I don't have a garage or a driveway to work on it. But, if you guys can think of any other suggestions, I'd really appreciate hearing them. I just may try to squeeze in a new throttle body if I can, before the weather gets too bad. But I would HATE to have to spend all that money on a new one, just to find out that that's not the problem...

I read over the thread twice but still did not read that you removed the Throttle Body and cleaned it. Have you done this?

In my experience, It is almost impossible to have a REP event with no code, very strange.

Unfortunately it's not getting any warmer, you should get the TB cleaned and those grounds checked out soon.

 

[fadyasha]

Disconnect your battery and clean the throttle body first before buying a new one. Also double check your coil packs again. I had one that was bad, so changed it. Before I knew it ended up changing another 3

 

[CaptainXL]

I would HATE to have to spend all that money on a new one, just to find out that that's not the problem...

Since there are no codes for it I doubt its the problem.

In the mean time it would make more sense to spend the $$$ to get the transmission fluid and all other fluids (diff/transfer case)changed if they need it.

Have you run any super strength fuel injector cleaner? I recommend you use a high tier fuel the next couple fillups along with some BG 44K.

These line of trucks can be one thing right after another if maintenance was never kept up. Eventually after going over everything you might get to the crux of the issue.

I wouldn't go too overboard on maintenance and just replace parts haphazardly. Could be costly. For instance I wouldtake pause, regather and check compression next if both the fuel and ignition systems check out. Could turn out your valves need work.

 

[pcharm129]

Ok, so here's what's going on with my truck now. During the blizzard last month, I pulled out of a parking space,on 62nd and Colombus Ave and drove to the corner of 61 and Colombus Ave. Noticed a lot of traction and stability loss and decided to try out 4Lo. I put the vehicle in 4Lo as I turned the corner and drove up 61st street. Traction and stability seemed to improve a bit. When I reached the corner of 61st street and Central Park West (2 blocks up), the truck stalled on me in the midst of a turn, a few seconds after my ABS and Brake lights came on at the same time. Afterwards, the truck successively continued this pattern about 5 times, between 61st and Central Park West and 68th and Central Park West. Each time taking between 5 and 10 minutes to restart. Ultimately, refusing to restart, forcing me to renew my AAA membership to have her flatbeded back to the parking spot I initially pulled out of. I have NO IDEA what the hell is wrong with this damn vehicle, and I'm almost ready to roll her off a cliff somewhere...:banghead: Presently, she's at the stealership (for the last 2 weeks) for a diagnostic, and THEY can't figure out what the problem is either!!! Their about to charge me an additional $136 if I want to continue past today or tomorrow! I just about at my wits end. They said something about a bent hub and that there's a voltage drop on the left side ABS or Brake sensor or something. I also just ordered a PCM from PCMFORLESS, because before I had them tune the installed PCM, I had a p0606 code on it, so I'm thinking that maybe the PCM is just all together failing. But now I'm going to have to have a CASE RELEARN done when I get the new PCM, which of course is yet MORE money that may be for nothing. I just replaced the damned throttle body cause a few mechanics said that that might be the problem (because of the throttle position sensor)! Smh! So if anybody here has any idea of what this issue might be or has any suggestions, I would REALLY appreciate it. Because I'm pretty much at the "screw this" point, and am ready to chop her up and sell her for parts!!!

 

[pcharm129]

I should also add that this condition does not occur unless the vehicle is in motion. It can sit in park running all day long without incident.

 

[CaptainXL]

I should also add that this condition does not occur unless the vehicle is in motion. It can sit in park running all day long without incident.

In motion not in gear, in gear or both? The shop should have enough info by now using a data logger.

 

[pcharm129]

In motion not in gear, in gear or both? The shop should have enough info by now using a data logger.

Well, I haven't really sat past around a minute or so with the car in gear, to definitely rule out both. But i HAVE let the truck run on auto start for about 20 to 30 minutes. And the condition never manifested. So I would strongly lean in the direction of the vehicle having to be in motion. And No, the dealer still claims not to know what the problem is. It's still not throwing any codes. They're trying to use psychology to infer that it could be the mods I did to her. Like I don't know anything about this truck, and haven't researched her to earth's end. Either because they're at a loss, or they're trying to get me for more $, or both. They said that they're charging me for 1 hr diagnostic [$136]. But if I want them to continue they will have to charge me more. NOW they're saying that they bill at $136/hr. But when I initially inquired about the price of a diagnostic, they told me $136, NOT $136/hr.)

 

[CaptainXL]

It's always a good idea to remove any aftermarket items from the truck before doing any serious intermittent troubleshooting like this. I know there a lot of bypass modules for remote starts that communicate over the OBD2 data port and could cause some issues if not working correctly. In cases like these it won't matter if you are skilled or not. If something isn't working right at an IC component level then it's out of your hands.

For instance I have an intermittent issue with my remote start draining the battery down to 50% after a few days. Still need to take it in to have the installer look at it. If I remove the power to it by pulling it's fuse then the drain disappears completely.

Your case almost sounds like a shutdown input from something like the motion/tilt sensor or malfunctioning brake switch is being activated at an inopportune time and disabling the remote start in combination with a remote start that is not relinquishing command when you press the brake pedal. Check the brake switch is working correctly. Sounds like that is the problem. Remove the remote start brain to diagnose.

 

[pcharm129]

It's always a good idea to remove any aftermarket items from the truck before doing any serious intermittent troubleshooting like this. I know there a lot of bypass modules for remote starts that communicate over the OBD2 data port and could cause some issues if not working correctly. In cases like these it won't matter if you are skilled or not. If something isn't working right at an IC component level then it's out of your hands.

For instance I have an intermittent issue with my remote start draining the battery down to 50% after a few days. Still need to take it in to have the installer look at it. If I remove the power to it by pulling it's fuse then the drain disappears completely.

Your case almost sounds like a shutdown input from something like the motion/tilt sensor or malfunctioning brake switch is being activated at an inopportune time and disabling the remote start in combination with a remote start that is not relinquishing command when you press the brake pedal. Check the brake switch is working correctly. Sounds like that is the problem. Remove the remote start brain to diagnose.

The remote start works as it should. I had my Viper 5901 installed from day 1, and haven't had a problem with it. I bought this truck in 9/2010. When the brake is pressed, the truck shuts off. The issue I'm having is not an isolated one. During my search for a cause, i've seen the same simultaneous Brake and ABS light issue complaind of before. But noone ever presented a solution. The dealer said he has seen it before himself. But claims that at that time, it was a fuel pump issue. My issue manifested as a jerking while accelerating (intermittantly/arbitraryily). The lights would come on simultaneously and the truck would start its nonsense, and sometimes the Reduced Engine Power light would come on. The truck NEVER had a problem starting before this past Feb. blizzard. And I never had a constant driveability issue, until then either. She did get hit by a police baracade earlier that morning. But on the passenger side. It was parked and I didnt see it happen. But what I surmise is that a Semi turned the corner where I was parked, and as it was straightening up, pushed the baracade into the front bumper, bending the reinforcement bar and cracking my damn SS bumper cover... When the police came to take the report, I tried to start her but she wouldn't. Later on that night after work she did start. But I think that when I put her in 4Lo, I may have complicated or accelerated an existing problem. (Shrug...) The dealer ALSO can't tell me why my driver's side rear window won't work anymore. They told me that the mechanic said that I need a new Regulator. But I know that's BULL... because I already tested it. Switches and all. If I apply direct power to the motor, I can roll the window up/dwn flawlessly. I explained to them that the issue is either with the signal wires from the module, or the module itself (below the rear seat fuse box). They told me that they never heard of a module below the rear seat fuse box. That the only module he knows of, is in the drivers wind/locks control switch in the door! I personally just think that their idiots and that I shouldn't have to pay them for a diagnostic, that drew a blank!!!

 

[christo829]

For the window issue, swap the controls from the non-working door to the working door, see if the problem moves with it.
If not, swap the driver's door module with the passenger's door module. Also, where did you apply voltage to the door motor?
If inside the door, then check the wiring between the door and body for a possibly worn wire. Might even be hidden in the insulation.
The door control modules are in the doors, not back by the interior fuse block. You might be thinking of the body control module?
There could definitely be a communication issue between the door modules and the BCM, but verify the wiring and the door modules first.
The door modules are more than just the window switches, and do communicate with the BCM, so if there's something interfering with
that communication, swapping the modules might help narrow that down to either door specific wiring or an individual module failure.

For the starting/stalling issue, there were a number of members on the old site who had their remote start units fail after
a period of time, with similar effects as what you list, though I don't recall any one having their trucks stall when applying the brakes.
For testing purposes, if you feel like taking the time, take the remote start out of the circuit, to eliminate that as a possible
contributor to the problem. Make sure that any interconnections are solid, not just something fun like wire nuts and electrical
tape.

Could it still be a fuel issue? Possibly. My old Lumina would run fine at startup, but 20 minutes in to driving, the fuel pump pressure would
drop to half what it should have been. That would show itself as a slow fluctuation in rpms while driving and stalling at lights when I went to hit the gas
to go again. I wish our trucks had active fuel pressure sensors that could be read. You might be able to check for this with a fuel pressure gauge
that you check at startup, and then later during a drive, but that's moot if you can't get the truck to start in the first place.

I'd lean towards pulling the remote start just to eliminate that possible problem vector.

Good Luck!

Chris

 

[pcharm129]

For the window issue, swap the controls from the non-working door to the working door, see if the problem moves with it.
If not, swap the driver's door module with the passenger's door module. Also, where did you apply voltage to the door motor?
If inside the door, then check the wiring between the door and body for a possibly worn wire. Might even be hidden in the insulation.
The door control modules are in the doors, not back by the interior fuse block. You might be thinking of the body control module?
There could definitely be a communication issue between the door modules and the BCM, but verify the wiring and the door modules first.
The door modules are more than just the window switches, and do communicate with the BCM, so if there's something interfering with
that communication, swapping the modules might help narrow that down to either door specific wiring or an individual module failure.

For the starting/stalling issue, there were a number of members on the old site who had their remote start units fail after
a period of time, with similar effects as what you list, though I don't recall any one having their trucks stall when applying the brakes.
For testing purposes, if you feel like taking the time, take the remote start out of the circuit, to eliminate that as a possible
contributor to the problem. Make sure that any interconnections are solid, not just something fun like wire nuts and electrical
tape.

Could it still be a fuel issue? Possibly. My old Lumina would run fine at startup, but 20 minutes in to driving, the fuel pump pressure would
drop to half what it should have been. That would show itself as a slow fluctuation in rpms while driving and stalling at lights when I went to hit the gas
to go again. I wish our trucks had active fuel pressure sensors that could be read. You might be able to check for this with a fuel pressure gauge
that you check at startup, and then later during a drive, but that's moot if you can't get the truck to start in the first place.

I'd lean towards pulling the remote start just to eliminate that possible problem vector.

Good Luck!

Chris

Hey! Thanx for the input christo829. In the case of the window, you're totally correct. I am referring to the BCM. My bad on the terminology. And I did swap out the rear switches. No change. The BCM leads to the problem rear window's switch measures present voltage in mV. But should be reflecting around 12 volts. As for the front switches, they are not interchangeable. I would need access to another driver side switch. Which I don't have at the moment. But all other functions are fine. Just that damned window. Oh, and I tested the motor, both, by applying voltage directly to the motor, as well as to the switch. Both work fine. (I previously asked for help with this issue here: http://gmtnation.com/f23/trailblazer-throttle-body-2002-both-rear-power-windows-out-3885/)

As to the starting/stalling issue, she doesnt stall when the brakes are depressed. She stalls as you are driving, once the ABS/Brake lights come on simultaneously. And when it does, you don't even notice until one of the notification lights (the battery light for example) comes on, or you try to accelerate and realize that she cut off, or that the power steering is out. There's no traditional vehicle shutter before it happens. Also, she only takes a while to start back from that immediate condition. If she's parked, she ALWAYS starts, with the exception of that one time I referred to, when it got hit in the blizzard last month. And as far as disconnecting the Viper, the best I can do is maybe pull the fuse from the brain and bypass module. Disconnecting all those wires is simply out of the question. That would have to be a last resort because I would have to take it to be reinstalled.

I recently checked the fuel pressure when I changed the fuel filter. It was perfect. As for monitoring it during a drive, how would I go about doing that? Please let me know. Thanx again for your input.

 

[CaptainXL]

Remove the 60 amp ABS fuse under the hood and drive it like that for while. In the mean time plan on getting the codes read from the ABS module. Some over on the OS had to replaced the ABS computer to fix issues like this. In some cases the ABS was unable to communicate with the scan tool. Not saying that is your issue but its time to start systematically eliminating non essential systems to narrow down possible causes.

 

[christo829]

Hey! Thanx for the input christo829. In the case of the window, you're totally correct. I am referring to the BCM. My bad on the terminology. And I did swap out the rear switches. No change. The BCM leads to the problem rear window's switch measures present voltage in mV. But should be reflecting around 12 volts. As for the front switches, they are not interchangeable. I would need access to another driver side switch. Which I don't have at the moment. But all other functions are fine. Just that damned window. Oh, and I tested the motor, both, by applying voltage directly to the motor, as well as to the switch. Both work fine. (I previously asked for help with this issue here: http://gmtnation.com/f23/trailblazer-throttle-body-2002-both-rear-power-windows-out-3885/)

As to the starting/stalling issue, she doesnt stall when the brakes are depressed. She stalls as you are driving, once the ABS/Brake lights come on simultaneously. And when it does, you don't even notice until one of the notification lights (the battery light for example) comes on, or you try to accelerate and realize that she cut off, or that the power steering is out. There's no traditional vehicle shutter before it happens. Also, she only takes a while to start back from that immediate condition. If she's parked, she ALWAYS starts, with the exception of that one time I referred to, when it got hit in the blizzard last month. And as far as disconnecting the Viper, the best I can do is maybe pull the fuse from the brain and bypass module. Disconnecting all those wires is simply out of the question. That would have to be a last resort because I would have to take it to be reinstalled.

I recently checked the fuel pressure when I changed the fuel filter. It was perfect. As for monitoring it during a drive, how would I go about doing that? Please let me know. Thanx again for your input.

AH..my bad...I meant swapping the door modules. Those are interchangeable, and might help narrow down the communication culprit. The switches you can probably just do a continuity check with a voltmeter. The odds of the BCM being at fault for one window are pretty slim compared to the odds of it being bad wiring or a failing module. The communication wiring will measure mV, but you should be able to get 12V on the main. Also, verify a good ground connection.

Fuel pressure....what I did to check mine was merely check it when I first started the car, then checked it again when I reached my destination, before I shut the car off.
When the car was first started, I'd have 50psi (good for that model). By the time the car had warmed up and I'd driven for 20-30 minutes, it had dropped to 25psi.

Remote Start...these trucks are really finicky about their electrical signals, so I tend to be suspicious of anything that cuts in to wiring that might allow noise in to the data bus at any point. I'm not certain that disabling the Viper brain would really be eliminating the possibility, but if the brain is generating unwanted signal on the data bus at any point, that could cause the PCM some degree of confusion.

I'm assuming you've checked all the grounds?

Ever changed the ignition switch? That's a WAG on my part, but there is the possibility that there's more than one issue causing the stalling. I didn't see it in the list of things
you had already changed, but I may have read over it. Most of the other items I can think of that might contribute to the stalling would also generate codes that the stealership should be able to see quite readily, so I'm ttyinhg to consider the stuff that doesn't code.

Cheers-

Chris

 

[Solraven]

This seriously sounds like a grounding issue. Replace your ground cable please extra grounding straps between the body and frame and between the engine and the frame you might not be able to see but they might be partially rotted out and it's going to be an intermittent issue you'll never be able to tack down.

 

[Mooseman]

You do realize you're responding to a 7 year old thread?