Chev trouble codes

'95 chevy 1ton 4x4 7.4 tbi VIN engine code N
Truck dies at stop when in gear(D or R) and stumbles when in P or N. Runs normal when driving.

So I am pulling code 12,36 and 42.

12 is normal -system acknowledgment

My chiltons says 42 is ignition control- probable cause-PCM has an open or grounded IC or bypass circuit. Will be replacing ignition control module tonight.

The book says nothing about a code 36, its not even listed. Anyone know what this is?

this is what I found about code 36:

"ECM detected less than 40 high resolution timing pulses
between each low resolution pulse for 5 consecutive cycles"


I hope this helps...

Do you know if it is ODB-I or ODB-II? Apparently, there are some late 95 model year vehicles that have ODB-II on them...

OBD-1

Zoediak, I saw something similar to that for the diesel trucks. Perhaps it is related to the ICM since it has to do with timing pulses.
Thx

no problem...

I found that error for both the 5.7's and the 7.4's:awesomework:

Zoediak said:

this is what I found about code 36:

"ECM detected less than 40 high resolution timing pulses
between each low resolution pulse for 5 consecutive cycles"


I hope this helps...

Click to expand...

Thats for the diesel motor--talk about a curve ball :haha: :haha:


Devon--do you have an actuator on the throttle body? Thats what 36 is for...

Oh and on the code 42

Code 42 can also be set if the est/bypass wire is disconnected to set the times. But if thats not the case---code 42 is one of the hardest codes in OBD I to diagnose.. It can be the ignition module/ecm/pcm or wiring...

I'll check the wire. I have a spare ICM so I will try it.

As for the actuator, is that the vaccum actuator just in front of the throttle linkage or something else? I can post a pic if that helps.

426rider said:

I'll check the wire. I have a spare ICM so I will try it.

As for the actuator, is that the vaccum actuator just in front of the throttle linkage or something else? I can post a pic if that helps.

Click to expand...

Get me a pic. And its IAC--not ICM :awesomework:

Ignition Control Module (ICM)is what I have a spare of . I already replaced the Idle Air Control(IAC). Ok Pic coming in about 10 min.

426rider said:

Ignition Control Module (ICM)is what I have a spare of . I already replaced the Idle Air Control(IAC). Ok Pic coming in about 10 min.

Click to expand...

AHHH--We never used ICM until we got the vortecs---the module was seperate from the dist at that point.... I would clear the codes and see if the 42 resets..

OK OK so the motor is a lil dirty. Little brown wire under dash is plugged in.

Drivers side

Passenger side

Top view

The thing right next to the PCV valve is called the "idle speed control actuator solenoid" Is that what your talkin about? It is connected via vac line to the vac dohickey under the throttle linkage.

Thats it. check to make sure you have manifold vacuum source to the control soloniod(follow the vacuum feed line from the actuator). Key on make sure you have voltage on pink/black wire. Hook up a vacuum pump and with key on--ground the dark green wire and see if the soloniod clicks and make sure you gt vacuum thru it(to the actuator)...

426rider said:

The thing right next to the PCV valve is called the "idle speed control actuator solenoid" Is that what your talkin about? It is connected via vac line to the vac dohickey under the throttle linkage.

Click to expand...

yup yup

thanks, going to check it out and clear codes.

Idle speed control actuator solenoid seems to be working. It clicks when grounded with vac pressure or without. After clearing codes I am getting nothing right now. Will take it on a longer drive when the kids wake up from their nap. Still dieing when put into gear

Take off the IAC and the EGR and clean them. Look for Carbon deposits in the EGR holding the pintle open. Also look when you put the egr back on that the intake vacuum hole is on the pintle side of the egr. The egr can be installed backwards and then the intake vacuum will pull the pintle off it's seat and allow exhaust into the intake, causing your problem.

View attachment 10225

The EGR and the IAC are both new. I will pull the EGR to make sure its on the right way.

The CTS and O2 are also new. New plugs, wires, exh man gaskets.

Thanks for any help

Next step---lower the ecm. start and let the rig idle and let it get hot---take your hand and slap the ecm flat handed (like spanking a kid) and see ifit stalls.. Sounds funny but I have nailed ALOT of ecms this way..