p0236 and p0238 codes

[stacks04]

Problem: Explain your problem in concise language (ie: Cranks but won’t fire). p0236 and p0238 codes


Demographics: tell us about your truck and your ambient conditions:

- Year: _1997_____
- Truck model and class (ie: c2500) __k2500 suburban_______
- Automatic or Standard __auto________
- Mileage: (indicate miles or km) ___115k______
- Replaced parts and mods (IP, PMD, chip/PCM, TM, injectors etc) ___relocated driver________
- Model: ‘S’ or ‘F’ engine, NA or Turbo, EGR? _____f_________
- Ambient outside temp: (indicate *C or *F) __60's________
- What fuel are you using? (#1 Diesel, #2 Diesel, Bio, VO, WVO, etc) __bio_______
- What fuel additives are you using? ___n/s________
- Where are you located? _____ct________

General maintenance: inspect and evaluate the condition of each. When were they last changed?
- Air filter ___recent______
- Fuel filter ____"_____
- CDR Valve? ___n/s______
- Coolant – last flushed/replaced at _____recent________
- Oil – synthetic/regular, changed at ____recent_______
- Batteries – state of charge, (matched set) replaced at ______good_______
- Battery cables and grounds (removed, cleaned and tightened): _____good_________
- Glow Plugs - how many miles on them? ___n/s______ What type? _____gm________
- Injectors - last changed at ______n/s_________


History: (Describe how the problem first appeared.)
- What were you doing when it happened? ____towing__________
- How was the truck running fine before this problem appeared? _____fine________
- Has this problem ever happened before? ________few times_______________
- Describe any related factors that might be part of the problem. ______________
- Have you checked for DTC (Diagnostic Trouble Codes)? (Y.N) _y___ And? ___p0236 p0238_____


Diagnostics:

1] Starting:
1a] Does the engine start? ___y______
1b] Does the engine crank over? ____y____
1c] Are your batteries fully charged? __y_______
1d] Have you removed, cleaned, and tightened all battery connections? ____y____
1e] Does your Wait to Start light come on for a time? How long? ____few seconds_____
1f] Does your glow plug light come on? _________ For how long? _________
1g] Do you see smoke from the exhaust while cranking? What color? ___n_____

2] Fuel Issues (if not running):
2a] Can you hear your lift pump working? ____________
2b] Do you get a steady flow of fuel from the water drain (T-handle) ? _________
2c] Loosen the inlet line from the IP – is fuel coming out (Lift Pump on)? ___________
2d] Loosen an injector line and crank the engine - does fuel come out? _________
2e] Do you hear a vacuum (hiss) when you remove the fuel cap? ___________

3] PMD / IP Issues
3a] Location of PMD (on pump, on intake, remote mounted) ___________
3b] Condition of Extension harness (if used) Vendor or Homemade? _________
3c] Condition of grounds / ground wires to IP / PMD. Check Harness. _________
3d] PMD Make: ___________
3e] PMD Age: _____________

4] Stalling Issues
4a] Do you experience stalling only when hot? ____________
4b] Does it stall under particular circumstances? (ie hit bump, or on accel) ______
4c] Does pouring cool water over the IP seem to help with restarting? _________
4d] Is stalling momentary (engine recovers)? _________
4e] Does SES light come on when engine hiccups? _________
4f] Does cruise control quit working when engine hiccups? ___________
4g] Does re-starting seem to reset engine, restoring cruise and power? _________
4h] Changes to dash lights or instruments during stalling events? ___________

5] Running Issues
5a] On cold start, does upper rad hose get hard before engine warms up? _______
5b] Any bubbles or oil film in coolant overflow tank? _______
5c] Any white slime on oil surfaces (dipstick, CDR, oil Fill cap)? __________
5d] Excessive white smoke from exhaust on cold start? _________
5e] Excessive black smoke from exhaust under hard acceleration? __________

6] Performance Issues
6a] Do you have gauges? ____no_______
6b] Maximum boost under load? _____n/s_______
6c] Have you added a performance PCM (reflash) or Chip? _____no_________
6d] Have you changed exhaust / downpipe / crossover? _______no_________
6e] Wastegate – mechanical or vacuum? ____vacuum__________

7] Temperature-related Issues:
7a] Single or dual thermostats? ____________
7b] Have you replaced them lately? Manufacturer of replacements? _________
7c] Have you pulled and cleaned Radiator and coolers lately? ____________
7d] Have you replaced the fan clutch? Manufacturer of replacement? ________
7e] (winter) Have you tested your antifreeze? Good to what temp? __________
7f] (winter) Are you using a winter grille cover? ___________



thanks guys, not much of 6.5 guy, got into diesels after the duramax so i am not up to speed on the older stuff. i know the codes are a signal voltage high and turbo performance. just not sure where to start. it is a side job i have and i drove it many times and cant get it to act up, it only does it while towing. any questions ask away. thanks joe.

 

[toddlnrd]

I assume this truck still has the original vacuum system to control the turbo waste gate.

IIRC, the P0236 is the waste gate solenoid failure, not sure about the other.

Todd

 

[Turbine Doc]

Stacks, WG/Turbo output on the 6.5 is vac controlled, vac pumps often die, check there 1st see if vac pump is making vac, then check lines to make sure not cracked, what is 8th digit of your VIN S(EGR) or F if F only one solenoid to the WG actuator, output of it should have 15+ vac on it.

WG on the 6.5 should always be closed (pulled into the can), boost is lowered by PCM command to open the WG less vac applied so less drive gas to run the turbo up & less boost made. At Idle you should not be able to move the arm on the wg, with both codes that sort of indicates a loss of vac problem.

 

[Turbine Doc]

Okay I re-read 1st list I forgot we ask S or F there, so only 1 solenoid and easier to TS the vac fault, sometimes WG can be "fixed" by spraying WD-40 into the ports, but if you have to do that it's a band-aid, needs a new solenoid soon, you can tee into the solenoid outlet to the WG snake a long hose into the cab attached to a vac gage, (don't pinch the tube and deadhead reading).

 

[stacks04]

so i should have full vac at idle at the waste gate actuator. 15" or so, if not check vacuum source. and vacuum valve for operation.

what are the possibilities of it being electrical or pcm related?

 

[Turbine Doc]

slim probability;

electrical in that solenoid itself is bad, or maybe a gnd issue, most common fault however is loss of vac either in total, or from solenoid not working properly, there have been some bad diphragms on actuators as well. If it's bad vac pump can be corrected with mechanical vac control, IMO best to use that anyway as it removes a weakpoint it the 6.5 system see here http://heathdiesel.com/T/Chevy-GM/Chevy-9601/Turbocharger-Boost-Controllers/ remove the vac pump, run shorter drive belt, vac solenoid goes away, plumbing issues as well, truck makes more power, you could build one but then you would have to test spring tension to know correct spring tension for spring chosen for the "home-brew" version, the Heath TM is a set & forget item well proven many trucks, of course next best is to get rid of the GM turbo and move up to the ATT.

 

[mitchedo]

In my case, once I replaced the stupid $400 vacuum motor due to a blown diaphragm, I was still getting a boost code. Vacuum was good, but when I hooked up my AutoEnginuity and went for a drive, I could see that the solenoid was acting up. I whacked it with a screwdriver, and problem solved. I have since replaced it.

I can't imagine troubleshooting these things without real-time readings from the sensors. You'd just have to replace parts and hope you get the right one.

Check for vacuum at idle at the solenoid and at the vacuum motor (wastegate actuator), and check that the vacuum motor holds vacuum. If those check out, then replace the solenoid. If it's still acting up, you could replace the MAP sensor, but it might more likely be in the wiring for the solenoid. ...or the wastegate itself could be hosed inside the turbo housing.

 

[stacks04]

okay guys, got full vac at idle in the pump side of the switch along with the pulse side of the switch. at the waste gate though it is only reading 3-4 lbs. it does pull the gate into the can completely but it takes a few seconds. i put 15 lbs of pressure on the line to check for leaks and it holds???? and it holds 15" of vacuum when applied by my hand pump. maybe the actual vacuum connector is leaking on the solenoid?

 

[Turbine Doc]

or filter in the solenoid itself is plugged, or plunger in coil ain't moving like it should, for test only direct plumb the turbo direct to the turbo wg actuator, once plumbed you should not be able to move WG are, and plunger should suck all way in, I once had slow leak at diaphragm, and could not make full boost, so plumb direct and go for drive see if it will hold 10 psi boost, will make more but don't push it hard to see if it will, if it holds then that goes to the solenoid not doing it's thing, sometimes band-aided with WD-40 sprayed into the solenoid, but that fix doesn't last long and you need new solenoid.

 

[Turbine Doc]

You can wire the WG shut until you get new solenoid, just don't beat on it 6.5s don't like high psi boost without some post turbo cooling, so if exceeding IAT it will defuel on you, plus a lot of exhaust backpressure on a fully shut WG, mpg also suffers with fully shut wg.

Since this is a F engined truck, scrap the vac system/vac pump, run shorter belt and add in a TM http://www.heathdiesel.com/T/Chevy-GM/Chevy-9601/Turbocharger-Boost-Controllers/

 

[JMJNet]

Try to replace the WG Solenoid, you should be fine.
That is another weak point, although sounds like it lasted more than 10 years.

Erase the code and see if it shows back up.

 

[stacks04]

i did some more tinkering and if i dik around with the vacuum connector on the solenoid it will make pressure at the w/g. i think i am going to order the solenoid and tubing for now. i dont have time to install the mechanical in the next 3 days before he goes on vaca with it. i told him about the kit and he sounded interested so maybe over the summer once i have more time. thanks for all your help guys. i learned something new from you folks.

 

[96 OILBURNER]

Run a piece of hose from the solenoid to w/g. Cheap way to check for leaky tubing.

 

[Matt Bachand]

i did some more tinkering and if i dik around with the vacuum connector on the solenoid it will make pressure at the w/g. i think i am going to order the solenoid and tubing for now. i dont have time to install the mechanical in the next 3 days before he goes on vaca with it. i told him about the kit and he sounded interested so maybe over the summer once i have more time. thanks for all your help guys. i learned something new from you folks.

Solonoid was only about 30 bux I changed mine a few years ago. But it coded me I think. I had tons of black smoke too.

Since then I ditched v-pump all together and installed TM. No problems now to be had.

 

[BigArt]

Ditto :iagree:

 

[Justint]

Ok guys hope some of you are still alive and kicking @stacks04.. So I have the p0236 and shitty time towing on minimal hills.. goes into dtc and defuels. I have vac pump delete and tm... issue is.. the code p0236 is reading because the vac hoses are cut off at the solenoid (f vin) at least I believe that's why . Without towing, runs fine anywhere .

 

[Justint]

@Turbine Doc

 

[ak diesel driver]

what's your max boost? Stock tune? need more info

 

[Justint]

@ak have boost turned down to 9.5.. still defuels only when hauling trailer . Stock tune..

 

[Justint]

@ak diesel driver