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1995 K2500 - $1k Facebook Find

I received my OBD1 GM tester the other day and tested it tonight while I was supposed to be packing my tools for some weekend work.

Codes 22, 25, and 63 came up. I'll check what that means when I have a moment, but doing a quick search, I didn't see anything pop up from the combination of the 3.

If it really is 3 separate codes, it looks like a bunch of potential sensors.
 
Depending on where I look:

DieselHub:
22: Accelerator pedal position 1 circuit low
25: Accelerator pedal position 2 circuit high
63: Accelerator pedal position 3 circuit high

ChevyForum:
22 tps sensor signal voltage low
25 air temp sensor sensor out of range, high
63 oxygen sensor right side circuit open or map sensor out of range

OBD-codes:
23- intake air temperature (iat) sensor circuit (fuel-injected models)
25- intake air temperature (iat) sensor or circuit - high temperature indicated (1991 and later models)
63- manifold absolute pressure (map) sensor voltage high (low vacuum detected)

Troublecodes:
21/22grounded WOT circuit
22TPS out of adjustment
25MAT circuit
63MAP sensor voltage high

Repairpal:
22Throttle position sensor error (signal low)
25Intake air temp sensor error (high temp indicated)
63Right bank O2 sensor circuit error / MAP sensor circuit signal voltage high (low vacuum indicated)

Sure glad I got that narrowed down... :banghead:
 
Actually - I haven't replaced the injector harness before the PMD - and after a VERY QUICK search, it appears that should be the first thing I replace.

I'm also hoping that the pedal I bought off ebay is not a dud.
 
So...I could potentially change out the IAT relatively cheaply and easily (I'm assuming on the easily.)

It appears that the 6.5 doesn't have MAP but does have a boost sensor? But, I have a new PMD that has the resistor in it, so would I still need that boost sensor?

If I get the truck to start, I plan on modifying the vacuum wastegate into a manual wastegate - would I still need a boost sensor at that point?

Surely the boost solenoid wouldn't need replaced? I mean the boost sensor is already close to $100.

I wouldn't think the boost sensor would prevent the truck from running, regardless.
 
Without the boost sensor, the SES lamp would be lit up.
Looks to me that the only items that would cause the engine to not start would be the TPS or the pump driver module.
 
MrMarty51 said:
Without the boost sensor, the SES lamp would be lit up.
Looks to me that the only items that would cause the engine to not start would be the TPS or the pump driver module.
Click to expand...

Trying to confuse me with the pump driver module. You are talking about the PMD, correct?

PMD is brand new (well, new from Leroy). The injection pump harness is not. Can't blame the PMD until I update the harness.
 
treegump said:
Depending on where I look:

DieselHub:
22: Accelerator pedal position 1 circuit low
25: Accelerator pedal position 2 circuit high
63: Accelerator pedal position 3 circuit high

ChevyForum:
22 tps sensor signal voltage low
25 air temp sensor sensor out of range, high
63 oxygen sensor right side circuit open or map sensor out of range

OBD-codes:
23- intake air temperature (iat) sensor circuit (fuel-injected models)
25- intake air temperature (iat) sensor or circuit - high temperature indicated (1991 and later models)
63- manifold absolute pressure (map) sensor voltage high (low vacuum detected)

Troublecodes:
​
21/22grounded WOT circuit

​
22TPS out of adjustment

​
25MAT circuit

​
63MAP sensor voltage high


Repairpal:
22Throttle position sensor error (signal low)
25Intake air temp sensor error (high temp indicated)
63Right bank O2 sensor circuit error / MAP sensor circuit signal voltage high (low vacuum indicated)

Sure glad I got that narrowed down... :banghead:
Click to expand...
Ignore everything past the Diesel Hub entry. All of those codes that deal with MAP, IAT or TPS are for GASOLINE engines! The Diesel Hub codes are for DIESELS, and as such indicate that either the pedal position sensor unit on the throttle pedal is bad, or that there is a connector/wiring issue. The sensors themselves are known to go bad. That right there is a major cause of No-Start, as the ECM is not receiving either any voltage, or too low of voltage, from the throttle pedal position sensor to command the FSD to fire the IP.
 
MrMarty51 said:
Anxious to see this truck running.
Click to expand...

You and me both.

I told my wife that I was hoping for better weather than 39F and 90% chance of rain and she thought I was crazy for considering on working on it regardless of the weather since I'm recovering from a cold..

She's not the only one that's reacted like that, and I don't know why people don't understand that we can't always wait for perfect conditions to work on stuff.
 
Power with key on engine off. Just test voltage to ground each wire incase anything silly is happening. It has been so long I really don’t remember exact voltages and which wire. But if you are getting over 6volts anyone of them, hit the brakes and post here before plugging in the new one and one of the better brains than me might know off top of their head or I can find a book and start digging.

I really would not expect any issue. TPS doesn’t go out often, but they do just wear out. Crazy rare one to be electrically damaged.
 
@treegump are you talking TPS or TPPS? BIG difference!

TPS is the Throttle Position Sensor that mounts on the side of the mechanical IP that uses a physical throttle cable on '93 and earlier 6.5's.

The TPPS is the Throttle (Accelerator) Pedal Position Sensor that mounts along side the Accelerator Pedal next to the transmission hump and has a wiring harness plugged into it and is found on all '94 and up 6.5's that have an ECM & PMD and are "drive by wire".

Since this problem is with the '95, it does NOT have a TPS on it (IP mounted), it has a TPPS (Accelerator Pedal mounted).

The codes that you listed are all TPPS related (see your and my posts above about your 'confusion' and what those codes inferred) as to your problem and what symptoms would result [no start] and a couple of quick checks.

The TPPS can go bad. Early production '94 Model Year 6.5's had a two sensor TPPS and if one of those went bad, the resulting signal to the ECM/PCM put the motor into a WOT 'run away' input to the PMD/FSD. GM halted production until the wonks could figure out what was happening and how to fix it. The answer was to go to a three sensor TPPS and reprogramming the ECM/PCM to kill the engine, not go WOT, if it received a faulty signal from one of the three sensors.

That's what the codes you pulled indicate, one sensor not reading the same as the other two in the TPPS assembly on the Accelerator Pedal.
 
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