Throttle body (TB) relearn (4.2)

[gmcman]

Hope it's not a re-post but here's what works.

When you clean your TB generally you need to pull the wire harness but some may leave it attached. Either way, the PCM needs to re-establish the idle position after the gunk has been removed from the bore. This may or not be 100% accurate since the elapsed times are not set in stone.


Prior to the cleaning, it's best to unhook the NEG battery cable first. Disregard the cleaning if you only wish to perform the relearn.

Unhook NEG battery cable, remove harness from TB, perform cleaning.

Attach TB harness, after about 30 min of having the battery unhooked, re-attach NEG terminal.

Turn key to ON with all the dash lights on. DO NOT START AND DO NOT TOUCH GAS PEDAL. TB will perform series of noises during this time.

Leave key ON for about 5 minutes. DO NOT turn key off. DO NOT turn key off for the duration of the relearn

Start engine, DO NOT TOUCH GAS PEDAL, let idle for about 8-10 min.

Once engine has fully warmed, idle should settle around 600-625RPM. Generally under 650 RPM.

 

[Mooseman]

Nice article. Some of us don't like disconnecting the battery because we lose radio settings and presets. Would you know which fuses to pull instead?

 

[gmcman]

Fuses 10 & 28 are the PCM, However I have not checked for absence of voltage at the PCM with these two removed. The cooling fan is on fuse # 20 and the TB shares the 5V reference from the cooling fan so it's hard to say if 10 & 20 completely remove voltage from the PCM.

I'm assuming they do, just haven't verified.

 

[dmanns67]

Thanks for the heads up. I usually go the route of pulling #10 and #28 as well. If you get a chance to verify, please let us know.

 

[UMEXT]

Nice article. Some of us don't like disconnecting the battery because we lose radio settings and presets. Would you know which fuses to pull instead?

I don't like disconnecting the battery because the actuators like to stick in heat afterward, and it's August in Florida. Any ideas on how to avoid that?

 

[gmcman]

I don't like disconnecting the battery because the actuators like to stick in heat afterward, and it's August in Florida. Any ideas on how to avoid that?

That makes sense, can anyone confirm complete voltage removal from the PCM with fuses 10 & 28? If that's the case then perhaps we can edit the procedure. Don't want someone with actuators on their way out to end up having problems.

 

[HARDTRAILZ]

I need to do this. Since my last cleaning, my idle has been hovering around 1000 and bugging the shit out of me.

 

[AtlWrk]

That makes sense, can anyone confirm complete voltage removal from the PCM with fuses 10 & 28? If that's the case then perhaps we can edit the procedure. Don't want someone with actuators on their way out to end up having problems.

Looking through the schematics only fuse 10 would need to be removed. All the other fuses (including 28) only provide power when the ignition is turned to something other than OFF. The 5V reference to the cooling fan is provided BY the PCM and is only for the fan speed sensor. The cooling fan fuse (#20) is for the solenoid in the clutch and does not tie into the PCM at all.

 

[Jtyler77]

That makes sense, can anyone confirm complete voltage removal from the PCM with fuses 10 & 28? If that's the case then perhaps we can edit the procedure. Don't want someone with actuators on their way out to end up having problems.

Thats what happened to me. Took the battery out, went to get a new one, put it in and killed the passenger blend door and mode actuators. Then cleaned the tb and pulled the fuses with good results. Fun times with that passenger blend door, I whipped out the sawzall and did some surgery.

 

[eutechnyx]

Would it be possible to edit this following fuse removal steps instead of battery disconnect??

 

[gmcman]

Would it be possible to edit this following fuse removal steps instead of battery disconnect??

I agree, I would be fine with @Mooseman changing the disconnect the Neg cable to removing fuses 10&28.

11 years ago I dont think we had many issues with stepper motors possibly being damaged upon reset.

 

[TJBaker57]

I agree, I would be fine with @Mooseman changing the disconnect the Neg cable to removing fuses 10&28.

11 years ago I dont think we had many issues with stepper motors possibly being damaged upon reset.

No need to pull fuse 28. Fuse 28 gets power from the ignition switch, the pink wire on terminal C. As soon as you turn the key off you have removed any power from fuse 28.


And if we are speaking of a V8 engine ECM then you need to pull ECM fuse 29.

 

[Mooseman]

Holy cr@p! Talk about a zombie post!