2015 Peterbilt 579 Paccar MX-13 - Intermittent No-Crank No-Start

Question

Getting a random no-start on my 579. It's completely intermittent. Sometimes I turn the key and it fires right up, other times I get absolutely nothing—not even a click from the solenoid. The dash goes through its sweeping motions and I have plenty of battery voltage (12.6V).

When it happens, I have to cycle the key 10 or 20 times before it finally decides to crank. I've checked the battery terminals and they are tight and clean. It feels like a software handshake issue or a bad relay, but I'm not sure where to start digging on this Paccar setup.

HinoHarold · Answer

It could be the Crankshaft Position Sensor. If the ECM doesn't see a sync signal, it might inhibit the start command. Throw a scanner on it next time it acts up and see if you're getting RPM signal while attempting to crank.

KenworthKai · Answer

✅ Confirmed fix: This is a classic issue with the firewall bulkhead connector. Trace the yellow start trigger wire from the firewall to the starter. On this model year, the pins in the bulkhead connector often vibrate loose or get corrosion. I bypassed the pin with a dedicated jumper or cleaned and tightened the female pin tension, and the truck hasn't missed a start in 3 months.

TacomaTess · Answer

Have you looked at the starter relay in the fuse panel? These 579s have a habit of burning the pins on the bottom of the fuse box. Pull the relay and look for melting or discoloration on the plastic. Also, check the fuse for the TECU.

2015 Peterbilt 579 Paccar MX-13 - Intermittent No-Crank No-Start

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