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Jared D
Jared D, ASE Certified Technician
Category: Chevy
Satisfied Customers: 1233
Experience:  Shop Supervisor at County Fleet
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Ok we put our 1999 chevy 6500 in the shop. they changed the

Customer Question

ok we put our 1999 chevy 6500 in the shop. they changed the timing sensor and said the truck is fine. well this weekend it started to act like it was laboring for fuel and then kick back up and the finally die. it has done it several time this morning... supposedly they checked all the fuel and oil pressure with gauges and couldnt find anything. pls help
Submitted: 7 months ago.
Category: Chevy
Expert:  Jared D replied 7 months ago.

The fuel pump wiring behind the glove box was already inspected right?

Customer: replied 7 months ago.
Expert:  Jared D replied 7 months ago.

Looking over the schematics there are only two things left that I can think of the check:

The engine will put it self in reduced power mode if it thinks the PTO is activated.

Backprobe the Power Take Off (PTO) input Dark Blue wire, circuit #538 with a Digital Volt Ohm Meter.
Watch the voltage on this circuit when the condition is present.
If the voltage drops low, the PCM will "think" that the PTO is engaged and reduce engine power.

The high pressure fuel pump uses oil presure. If there is some kind of oil pressure loss, either a restriction in the oil system from the oil filter or low quality oil it could be causing the high pressure fuel pump to cut out.

Expert:  Jared D replied 7 months ago.

Check engine oil level.
Verify engine oil pressure.
Check the Injection Actuation Pressure Sensor wiring and voltages.
The Orange wire is 5 V reference from the ECM.
The Yellow wire is ground from the ECM.
The Green wire is the signal voltage from the sensor to the ECM.
The sensor signal voltage should change relative to engine oil pressure.
Connect an oil pressure gauge (capable of 5,000 PSI) to the oil pressure test port on the high pressure oil pump.
Compare actual oil pressure to indicated oil pressure in scan data (if you have a compatible scan tool).

Expert:  Jared D replied 7 months ago.

I just wanted to check whether you need any additional help.

If you no longer need assistance, please don't forget to rate.

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