6.5L TROUBLE CODES

Hello,

My 1994 6.5L diesel 4x4 2500 Suburban is returning codes 17 & 18. Do you have experience with these codes? What components are likely to be at fault?

Thanks, John Macmorran

Hi John,

DTC 17 - High Resolution Circuit Fault DTC 18 - Pump Cam Reference Pulse Error DTC

17 relates to the Optical Encoder Sensor's ability to read a high resolution coded data track disc that rotates with the fuel injection pump's main shaft. This problem could be due to a bad encoder sensor or an electronic drive problem as indicated in the next paragraph. Red dyed fuel and some blends of home-brewed biodiesel can cause this too. Make sure you're running straight #2 diesel fuel…

GM suggests that for a DTC-18/P0251 (1996+ vehicle), the fuel injection pump would need to be replaced once eliminating a possible wiring problem. If the problem persists, they then suggest replacing the PCM computer. This is a problem related to the system's ability to read the Optical Encoder Sensor.

However, our experience has been that every owner of an electronic fuel injected 6.5L diesel should have a spare (known good) PMD/FSD (Pump Mounted Driver/ Fuel Solenoid Driver) replacement module, both to have as spare and to use when troubleshooting fuel injection problems.

In addition, having an extension harness and remote mounted module make it a lot easier to replace/troubleshoot these and several other related electronic trouble codes.