Reduced engine power light outta nowhere
- Thread starter Whoy
- Start date
im honestly thinking about buying a whole new throttle body. is it possible i damaged the throttle position sensor while cleaning it with the tb cleaner?MAY03LT said:
I doubt it since the light popped on out of nowhere. The only thing about buying a new one is if it doesn't fix it, you'll be right back at square one.
I have the day off tomorrow, so I will have those pics for you. Not much I can do about the rain except complain.
I have the day off tomorrow, so I will have those pics for you. Not much I can do about the rain except complain.
Man you can have it all! I'm itching to get some work done.
Are you ready to have some fun?
Recording the battery voltage before starting any tests is a good habit to get into.
Test 1 - Key ON Engine OFF - Touch both sides of the TAC fuse. If voltage is above 12v, move on to test 2.
Test 2 - Key ON Engine OFF - Black lead of meter to battery negative, red lead of meter to yellow wire at throttle body connector. I'm using a t-pin. You can unplug the throttle body connector to test, but do not force the probe into the connector pin.
Do the same thing for the brown wire in the throttle body connector.
So, in my 03, I've verified voltage through the TAC fuse, and since I have voltage at both TAC wires at the throttle body, I know the pcm input/outputs are ok. If you don't have voltage in either (or both) of the TAC wires at the throttle body, I'll unplug my pcm and show those. I try not to unplug things unless it's necessary.
This is my version of the DIY starting point for p1512. The test numbers are from the OEM service info, the numbers in parentheses are my order. So (1) Check the TAC fuse (2) check the TAC circuits at the throttle body. If voltage is present at the TAC wires in test 2, I skip (3) and go to (4) check for a sticky/stuck/broke tbody. We could go further by using a super test light to load down the TAC throttle body wires, but usually TAC issues are from broken wire(s) in the wiring harness.
Your mission, if you choose to accept it, is to test and record your voltage at the TAC fuse, and TAC wires at the throttle body. Those results will tell us where to go next.
Are you ready to have some fun?
Recording the battery voltage before starting any tests is a good habit to get into.
Test 1 - Key ON Engine OFF - Touch both sides of the TAC fuse. If voltage is above 12v, move on to test 2.
Test 2 - Key ON Engine OFF - Black lead of meter to battery negative, red lead of meter to yellow wire at throttle body connector. I'm using a t-pin. You can unplug the throttle body connector to test, but do not force the probe into the connector pin.
Do the same thing for the brown wire in the throttle body connector.
So, in my 03, I've verified voltage through the TAC fuse, and since I have voltage at both TAC wires at the throttle body, I know the pcm input/outputs are ok. If you don't have voltage in either (or both) of the TAC wires at the throttle body, I'll unplug my pcm and show those. I try not to unplug things unless it's necessary.
This is my version of the DIY starting point for p1512. The test numbers are from the OEM service info, the numbers in parentheses are my order. So (1) Check the TAC fuse (2) check the TAC circuits at the throttle body. If voltage is present at the TAC wires in test 2, I skip (3) and go to (4) check for a sticky/stuck/broke tbody. We could go further by using a super test light to load down the TAC throttle body wires, but usually TAC issues are from broken wire(s) in the wiring harness.
Your mission, if you choose to accept it, is to test and record your voltage at the TAC fuse, and TAC wires at the throttle body. Those results will tell us where to go next.
dude, that is awesome. thank you. ill start on it as soon as i get home. on the dmm ill have to find that setting. so i completely understand, if one those test shows less than 12 volts then that is where my problem is with all this? also i just thought out about this. does the tb work off the air being took in by the air filter? i just put on a universal k&n filter in my tblazer could that possibly throw things out of whack?MAY03LT said:
No prob. Snap a pic of your DMM and we'll tell you which setting to use. I don't know why they all don't have an autorange feature but it's whatev. Yeah, as far as DIY testing, we're looking for yes or no on voltage since most problems are open circuits. The REP light/P1512 wouldn't be caused by a filter.Whoy said:
BlazingTrails
Member
- Apr 27, 2014
- 19,409
DCV = Direct Current Voltage so you'll want to set it 20 volts which will be the 3rd dot to the left of off.Whoy said:
I disconnected this connector with the key OFF. It's a 7mm bolt. There's a lot of thread there, so be patient and don't force it off.
This is the pin that gets power from the TAC fuse. Again, don't force your probe in here. Just touch it politely.
Now I turned the key to RUN - black lead on battery negative and red lead on the t-pin.
So for GM test 7, my test (3), I have power at the pcm's TAC input circuit.
Another thing worth noting, if you have the key in run, and are probing either of the TAC wires at the throttle body, you can wiggle the harness in this area and see if you get voltage at the tbody. There have been numerous cases that I've worked on over the years that ended up with a pinched/broke/cut wire in this area.
Your turn to test.
Here's where we are up to this point.
This is the pin that gets power from the TAC fuse. Again, don't force your probe in here. Just touch it politely.
Now I turned the key to RUN - black lead on battery negative and red lead on the t-pin.
So for GM test 7, my test (3), I have power at the pcm's TAC input circuit.
Another thing worth noting, if you have the key in run, and are probing either of the TAC wires at the throttle body, you can wiggle the harness in this area and see if you get voltage at the tbody. There have been numerous cases that I've worked on over the years that ended up with a pinched/broke/cut wire in this area.
Your turn to test.
Here's where we are up to this point.
Well, that confirms the problem area. Based on the test results, there is an open between the TAC fuse and the pcms TAC input.
So you have a couple of choices on what to do.
-Unwrap the harness between the pcm connector and the front fuse box and look for/fix the broken PINK wire (that's what I would do).
-Splice in a new wire from under the fuse box to the pcm connector (which will bypass the broken wire).
Unfortunately I don't have any pics of the front fuse block removed or of the wiring harness ripped apart. You might be able to find some on trailvoy if you search for "pcm ignition 1".
I'll post up some pics of the fuse block from the manual tonight - I'm on baby duty at the moment.
So you have a couple of choices on what to do.
-Unwrap the harness between the pcm connector and the front fuse box and look for/fix the broken PINK wire (that's what I would do).
-Splice in a new wire from under the fuse box to the pcm connector (which will bypass the broken wire).
Unfortunately I don't have any pics of the front fuse block removed or of the wiring harness ripped apart. You might be able to find some on trailvoy if you search for "pcm ignition 1".
I'll post up some pics of the fuse block from the manual tonight - I'm on baby duty at the moment.
dla442
Member
First is a gummed throttle body will cause a rep light and would seem the engine just can do much on acceleration. Proper cleaning and procedure on cleaning should cure this problem. Battery disconnect before and disassembling and cleaning. Reconnect and let the blazer idle for 20 minutes or so without touching the accelerator pedal. 150k and never a cleaning a TB is like why did my piston rod break of the crank cause the oil was never changed. It's a must and should have been the 4th or 5th time cleaned t 150k. I do mine every 30k and it's still pretty clean at that mileage. Start from there..if you are getting other codes after cleaning are they old ones or new ones. Have them cleared and start fresh for any codes that may pop up.
Mounce
Member
MAY03LT said:
wow, thats intimidating, my car problem and baby duty alike haha. i got ahold of a mobile mechanic who thinks he can fix it. only 65 an hour which is way better than the shops around here considering i live in oil/gas boom town.
would it just be easier but more problematic in the future to just run a new wire?MAY03LT said:
The reason that I would open up the harness instead of adding a wire would be to inspect the other wires near the where the offending wire was broken. If I caught something else that needed attention, that could potentially save me (if it was mine) or someone else (whose truck I was working on) a potential headache down the road. Like I said a few posts ago, there have been plenty of reported cases of our trucks having broke wires between the front fuse box and pcm. Scumbags like the one I work for would say "who cares, if another wire breaks it's not our problem." Real freaking professional.
But, yes, it would be easier to just run a new wire and call it a day.
But, yes, it would be easier to just run a new wire and call it a day.
had that mechanic come out. he checked the wires and they were all good. replaced the tb and the cam position sensor. my girl is running. shaking a tiny bit i can feel when idling. was told there are airs in the line and that should fix itself. could of swore i was doing everything like you told me. but want to say thanks to all for their time. you guys are awesome.MAY03LT said:
only thing now after driving is seems to sputter a little when accelerating coming out a complete sfop and my service engine light starts blinking after i hit 30 and stops after going below it.
update: changed coil pack and all 6 spark plugs. now running just as good if not better!!!
Hello
I have a REP light that came on and I have a code p1515 and a p1512. I have replaced throttle body and throttle pedal I checked voltage at plug on throttle body and I have 12 volts on the yellow wire but only 5 on the brown wire. Please advise what else I can check to further diagnose this problem
I have a REP light that came on and I have a code p1515 and a p1512. I have replaced throttle body and throttle pedal I checked voltage at plug on throttle body and I have 12 volts on the yellow wire but only 5 on the brown wire. Please advise what else I can check to further diagnose this problem
BlazingTrails
Member
- Apr 27, 2014
- 19,409
Midnyteryder196
Member
following so i can go through and check the wires to tb.. had same codes come on tonight while cruising down the interstate.. climbing a hill at 72, it down shifted, then ses and rep lights came on.. it was only about 3 degrees out side also.. got pulled over and checked/reset codes and was all fine for the rest of the 20 mile trip, and the 50 mile trip back home.. so if it doesnt happen again here soon, might wait til it warms up to check the voltages..
