2015 Peterbilt 579 Paccar MX-13 - Intermittent No Start - SPN 639 FMI 9

Question

I've got a weird one on a 579. Randomly, the driver will turn the key and get nothing but a 'CAN communication error' on the digital display and the truck won't even click. If he cycles the key 5 or 10 times, it eventually catches and starts right up like nothing happened.

I've hooked up DAVIE and I see a bunch of timeout codes for the V-ECU and Engine ECU. I'm thinking it's a rub through in the harness, but I can't find the break. It seems more common when it's raining outside.

RegenRogerD · Answer

Have you checked the CECU? Sometimes the internal power relay in the Cabin ECU fails and drops the ignition signal to the engine side.

AudiAlex22 · Answer

Look at the bulkhead connector behind the clutch pedal area (or where it would be). Water tends to leak down the windshield and drip right onto that main harness plug, causing pins to corrode and lose CAN signal.

KenworthKai · Answer

✅ Confirmed fix: Found the 'star' J1939 CAN bus connector under the dash was loose and had green crusty corrosion on the pins. This was causing intermittent resistance spikes. Cleaned the pins with electrical cleaner, applied dielectric grease, and reseated all terminating resistors. Problem solved.

2015 Peterbilt 579 Paccar MX-13 - Intermittent No Start - SPN 639 FMI 9

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