2004 Chevrolet Silverado 2500 HD 6.6L no start hesitation mil lamp on

Truck Question:

I got 3 codes on my Duramax diesel engine that shows up intermittently:

P0193- FR Press Sensor Ckt High Voltage

P0405- EGR Vac Sensor Ckt Low Voltage

P0642- 5 Volt Ref 1 Ckt Low Voltage

These are the codes after the engine shutdown. After it cooled down, I can reset them and the engine will run fine until I hit a bump or climbed a rough road. I need some guidance on how to test these codes.

ATS Adviser:

A quick way to test these code is to go to the fuel pressure sensor located under the intake manifold shield on the fuel rail. There you will see 3 wires: dark blue wire which is the 5 volt reference signal, orange black wire for low ref or ground signal and the yellow wire for the sensor signal. At KOEO, check the values of both 5 vref and ground signals. If the 5 ref is out of range, confirm the reading at pin 33 at the ECM terminal. The ground signal could be verified also at pin 2 terminal at ECM terminal and making sure no ground reading is higher than 0.250 volt.

If both signals are within range, I would change the fuel pressure sensor with a new one. This will correct code P0193 which will cause the other 2 codes to appear.

Final Fix:

You are correct! I replaced the sensor after testing both both 5 vref and ground signals were OK. The truck has been running good for the past week. Great service!

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