[BuilderM]

New member here, 99, k3500, 106k miles, auto, Dually, bone stock, cab chassis flatbed....am perplexed on this one as well as 5 techs I spoke with, now these techs are not viewing the truck but that really matters little as the issue is very complex...started on a mild morning, glow plugs work and block heater was not required, 45 degrees, ran for 1-2 minutes, then stalled, no restart....fuel 3/4 full, lift pump verified operational, fuel cap good, no lines leaking, cracked injectors, no fuel...now plugged in code reader....po237, po238, boost sensor shorted and high open,...why would that shut down the pump?, next verified electrical values to sensor 4.97 volts, ground test good, signal to pcm/ecm, sensor tested against know good running other truck, (96, k3500), tested that sensor values way different, low resistance 1.52 ohms on all sockets, as suspected shorted, my best conclusion the signal feeds to the ecm directly, (gm schematic), 4.97 volts from grey line, to black (ground), green line is signal ....my thinking it overvalued the ecm and it dropped out, plus odd parameters are showing on scanner...plugged into 96 to verify test and it killed that truck aswell....can the ecm be reserected or rebooted or am I needing to replace...?

 

[Glagulator]

My guess the engine harness under the intake has problems.
Pull the intake and get it out and inspect. Don't put it back under the intake.
It will work running along the upper pass. side of intake.
Your 99 PCM should have security and will not let the 96 run for more than a second.
98-up have security.

 

[BuilderM]

Ecm still communicating with scanner and shows all dash indicators, Therefore still viable, the item transferred to the 96 was the sensor only, if it was faulty, as is suspected now, by no start and check engine light, same as 99, then wiring is excluded as culprit...

 

[Glagulator]

Does it run with the MAP sensor (boost sensor) unplugged?
Engine will run with it unplugged.

 

[BuilderM]

Neither now

 

[BuilderM]

The shorted boost sensor signal wire is only directed to the ecm, Thru no other sensors Per the gm schematic,

 

[BuilderM]

The 4.97 volts is in spec, as feed to the sensor, per gm, the 99 shows the codes the 96 show none

 

[BuilderM]

So the ecm is not providing a clean output to permit the pmd to signal the fuel solenoid, (in the spider), not the fuel shut off solenoid...to actuate the flow of fuel to the mechanical portion of the pump to the injectors....my thinking

 

[BuilderM]

Fuel shut off solenoid was pulled and bench tested as well as in place, tests good

 

[Glagulator]

The MAP signal wire (GRN) MAY be shorted to something and it runs thru the engine harness with the rest of the IP sensor and control wires under the intake. Unplug the 8 pin connector at the back of the engine and see if the short is still there.
Keep in mind that moving the harness around can change things and cause confusion.

 

[BuilderM]

why would the sensor then kill both trucks?, if wiring was an issue in only one?

 

[Tommygunner]

Have you tried replacing the boost sensor? If it is shorted internally it will raise havoc with the 5v PCM output. May possibly overloaded the internal 5v transformer circuit in the PCM.

 

[Glagulator]

Sorry, I'm not interpreting your responses correctly.
Will your 99 run with the MAP sensor unplugged?
Have you tried a different MAP sensor?
FYI - the engine will run with the MAP unplugged, but will set codes.
Are the ECM-B and ECM-I fuses good?

 

[BuilderM]

I did with the know good unit, no success, no start on either

 

[BuilderM]

All fuses good, tried it with it plugged in and unplugged , both trucks, no start

 

[BuilderM]

I’m fairly certian that it has affected the ecm, my ultimate question is can the ecm be reset or rebooted or are the ecm now unresolvable?

 

[BuilderM]

Another thought, I can’t be the first person with this issue, on no less than two trucks at once..?, so there must be an issue with this design as it permits a voltage spike in excess of the value that the ecm could expect to encounter from that particular sensor, and how to protect it from reoccurring????

 

[BuilderM]

The gm tech shook their heads at the question when posed aswell, but they both noted they have little 6.5 experience

 

[Tommygunner]

To re-boot the PCM simply unplug it for ten minutes. Then connect it back up. If that does not work then the PCM may be shorted. Have you put a OHM meter directly on the pin on the PCM that the green signal wire connects to? That would tell if the short is internal to the PCM

 

[BuilderM]

Also can one reset parameters for the ecm as some values are way off spec, my intake air temp on the 99 show -38 f, the 96 show 66 f, actual air temp....