trailblazer was running fine , had to replace battery, now vehicle will turn over but won't start. fuel pump is coming on( can hear the whinning), checked all fuses and relays, any suggestions as to where to begin? son-in-law said to replace mass air flow sensor, would that keep it from starting?
trailblazer won't start after changing battery
- Thread starter spdeplayer2
- Start date
Mounce
Member
How long was the battery disconnected during the swap? If for around 30 minutes or more, clean your throttle body. When the battery is disconnected for a decent period the pcm resets and it loses its tune for the dirty throttle body and thinks that it's clean. It learns the tune over time as the throttle body gets dirty.
I think it would start but run poorly with a bad MAF but I'm not sure. But where is the reasoning behind him thinking that a battery swap killed the MAF? Don't think I've read a case of one going bad on our rides.
I think it would start but run poorly with a bad MAF but I'm not sure. But where is the reasoning behind him thinking that a battery swap killed the MAF? Don't think I've read a case of one going bad on our rides.
gmcman
Member
- Dec 12, 2011
- 4,656
Just had this issue with our toyota sienna. I had the battery disconnected for about an hour, when I started the engine I could barely get it to idle at 400 to 500 rpm and was stalling out.
Cleaned throttle body and it fired right up. The learned idle was erased like Mounce stated and the crud closed off the factory programmed opening.
Cleaned throttle body and it fired right up. The learned idle was erased like Mounce stated and the crud closed off the factory programmed opening.
UPDATE. got up tis morning and got vehicle to crank by pumpping gas while starting but won't stay idled on its own
NateDG
Member
The other thing to watch for when having the battery disconnected is if you have the auto HVAC, the system will also lose its programming and sweep all the stepping motors for the air flow and temp blend control to relearn their positioning. I learned the hard way.
The gears will be put under a tremendous force load and crack allowing the motor to continue past the expected end point and potentiometer will get confused and just stop trying and shut that motor off. Usually happens most to the mode door motor which gives you your face or foot airflow. The results, at least for me, was no more face air. That's the front vents for those not in the "bizz" ;-)
The gears will be put under a tremendous force load and crack allowing the motor to continue past the expected end point and potentiometer will get confused and just stop trying and shut that motor off. Usually happens most to the mode door motor which gives you your face or foot airflow. The results, at least for me, was no more face air. That's the front vents for those not in the "bizz" ;-)
gmcman
Member
- Dec 12, 2011
- 4,656
You need to remove the throttle body and clean it, no way around it...both sides and make sure the edges of the butterfly are cleaned.spdeplayer2 said:
Very easy to do. When you reconnect the TB, turn key to on but don't start and don't touch the gas pedal, leave it like this for a minute or 2, don't turn key off then start engine without touching the gas pedal, let idle for a few minutes. ..don't touch the gas pedal for the entire process.
Mounce
Member
gmcman
Member
- Dec 12, 2011
- 4,656
Good to hear, go over the hoses also and make sure they are connected...big hose under resonator this can be overlooked upon reassembly , evap hose on front of TB, just to be sure there's no vacuum leaks.
Should have mentioned to pull fuse number 10 and 28 to reset PCM, I would leave them out for at least 5 min.
Also forgot to add....do you use a K&N? If so you may need to clean the MAF as the oil can affect driveability
Nevermind, you mentioned MAF but the 2003 doesn't have one. Not until 2006.
Should have mentioned to pull fuse number 10 and 28 to reset PCM, I would leave them out for at least 5 min.
Also forgot to add....do you use a K&N? If so you may need to clean the MAF as the oil can affect driveability
Nevermind, you mentioned MAF but the 2003 doesn't have one. Not until 2006.
Mooseman
Moderator
Just want to clarify something about the HVAC. Both the auto and manual systems use the same actuators so they will go through the relearn process if the battery is disconnected. And it doesn't mean that they will fail but could fail. If it was already on its way out, it would have failed eventually.
This may be a bit off topic but can they be swapped? I have manual controls. Could I swap and plug in an auto unit or would there be more involved?Mooseman said:
Mounce
Member
Literal answer, yes. Easy answer, no. Tons of stuff that you have to swap/install that wasn't there, missing wiring, sensors and such thus everyone that I've seen bring it up quickly ditch the idea when they hear about what all has to be done.HeavyChevy4200 said:
-Misread your question and answered it differently than I could have. But yes, way more involved.
been 3 drive cycles now since re-setting pcm and cleaning Tb, vehicle running better , but still having an issue with it not shifting correctly,usally between 30 and 50
also to add, check engine light still blinking and goes solid for a few secs, then starts blinking again
Mounce
Member
Does it stay on afterwards? If so, get the code read at a local parts store for free and report back. Without codes there's not much you can do besides throw parts at it and we don't believe in that here lol. (if it's preventable)
If it doesn't stay on I'd say keep driving it like normal until it stays on then get it read.
If it doesn't stay on I'd say keep driving it like normal until it stays on then get it read.
yes it stays on then blinks, then stays solid and then blinks again. got code read and it didn't give a code, just says"multible misfires detected" and 'pump motor circuit stuck open"
Mooseman
Moderator
it didn't give a code number
had the code read at O'reilly, and it didn't give a number so the employe said it won't tell him what was causing the misfire
had the code read at O'reilly, and it didn't give a number so the employe said it won't tell him what was causing the misfire
Mounce
Member
Well it detected the codes and gave him the definition of them. Random /multiple misfire is P0300. Not sure what the other is.
But, the random misfire is what's causing the light to flash. It should eventually become a specific code telling you which cylinder(s) are causing issues. I'm not quite sure what the fuel pump code means, maybe the pump is dying and causing the misfires. Someone else would have to confirm.
But, the random misfire is what's causing the light to flash. It should eventually become a specific code telling you which cylinder(s) are causing issues. I'm not quite sure what the fuel pump code means, maybe the pump is dying and causing the misfires. Someone else would have to confirm.
Mooseman
Moderator
That's why the actual code numbers are important for us to know. Which pump or circuit is failing might be a clue to what is going on.
Usually, after a while, the PCM pinpoints which cylinder is misfiring but it can't seem to do it now. Sounds like something with either fuel or air. Could be something related to the pump circuit, not supplying enough fuel and thus, multiple misfires.
Usually, after a while, the PCM pinpoints which cylinder is misfiring but it can't seem to do it now. Sounds like something with either fuel or air. Could be something related to the pump circuit, not supplying enough fuel and thus, multiple misfires.
BlazingTrails
Member
- Apr 27, 2014
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