Diesel Place banner

1 - 14 of 14 Posts

·
Registered
Joined
·
21 Posts
Discussion Starter #1
Hello,

The other day I noticed my truck (1999 3500 dump) was lacking power under load. Eventually it throw a P0236- Turbocharger Boost circuit. I checked the obvious. The switch and vacuum, free wastgate flap. All are good. I found that I am not getting a pulse signal to ground to activate the switch from the computer. I traced the wire back to the computer and have continuity through the wire. So is the computer bad or are there other sensors that tell the computer when to pulse? Any good places to get inexpensive stock computers if that is the case? this is only a work truck.

Thanks
 

·
Administrator
Joined
·
16,702 Posts
Hello,

The other day I noticed my truck (1999 3500 dump) was lacking power under load. Eventually it throw a P0236- Turbocharger Boost circuit. I checked the obvious. The switch and vacuum, free wastgate flap. All are good. I found that I am not getting a pulse signal to ground to activate the switch from the computer. I traced the wire back to the computer and have continuity through the wire. So is the computer bad or are there other sensors that tell the computer when to pulse? Any good places to get inexpensive stock computers if that is the case? this is only a work truck.

Thanks
I would start by going back through all grounds. Remove each one, clean then re-install
The Wastegate Solenoid is a failure point.
You can get a replacement ECM through RockAuto but you will need to be reprogrammed.
 

·
Registered
Joined
·
3,171 Posts
MAP or boost sensor in the manifold also controls boost. If it goes bad it will throw a 236 code. Might want to check that also. Computer wont open (or ground pulse) the boost solenoid without input from the boost sensor
 

·
Registered
Joined
·
4,034 Posts
The signal from the PCM for the WGS is a PWM ground, the pink wire is 12v. ign.
 

·
Registered
1995 GMC Suburban
Joined
·
17,872 Posts
Are you sure it has good vacuum tubes?
If it is still original GM plastic, just replace them with rubber vacuum tube.

The wastegate solenoid is also problematic.

That is why I put a mechanical wastegate so I don't have to deal with this issue for 13 years now.
 

·
Registered
Joined
·
21 Posts
Discussion Starter #6
Thanks Guys!
  • Changed the boost sensor this morning and it did not help.
  • Will take a closer look at the grounds but I am not having any other trouble with the truck so I do not believe it is a ground issue.
  • Yes I have 12 on the pink wire, I know the computer pulses through the ground. PWM? not sure your terminology.
  • Yes, I know I have ample vacuum. If I jump the switch to ground the waste gate opens. How does it operate manually a mechanical wastegate?
 

·
Registered
Joined
·
4,034 Posts
Pulse Width Modulated = PWM
 
  • Like
Reactions: OkDually

·
Registered
1995 GMC Suburban
Joined
·
17,872 Posts
Check the FAQ for mechanical wastegate.
The early version of this diesel uses it.
 

·
Registered
Joined
·
3,171 Posts
236 is a problem with the electrical circuit. Check if you are getting 5V from the PCM to the boost sensor.
Check the main PCM ground on rear passenger side intake manifold bolt. Should have 3 wires going to it and clean.
 

·
Registered
Joined
·
21 Posts
Discussion Starter #10
Just checked PCM and have 1.5v with ignition on to battery ground. Still have to check that main ground.
 

·
Registered
Joined
·
21 Posts
Discussion Starter #11
The 1.5v was with just ignition power. I will start it and recheck it at idle.
 

·
Registered
Joined
·
21 Posts
Discussion Starter #12
Problem SOLVED. One of the ground wires on the back of the engine had broken free. Thank you very much for pointing me in the right direction.
 

·
Administrator
Joined
·
16,702 Posts
Problem SOLVED. One of the ground wires on the back of the engine had broken free. Thank you very much for pointing me in the right direction.
Glad you found the issue.
Thanks for giving us an update!
(y)
 

·
Premium Member
1995 Chevrolet Silverado Z71 6.5 TD
Joined
·
189 Posts
You guys on this site are all awesome...
 
1 - 14 of 14 Posts
Top