2021 Peterbilt 579 - PACCAR MX-13 - P0606 FMI 1 ECU Internal Error

Question

My truck is stuck in derate and showing a red stop lamp on the dash after a cold start this morning. I hooked up DAVIE4 and I am getting a persistent P0606 FMI 1 code indicating an internal microprocessor error in the PCI. The truck will start, but it has no throttle response and won't move out of the yard.

Dave Kowalski · Accepted Answer

The issue ended up being an internal failure of the PCI (Engine ECU) itself. After verifying that constant power, switched power, and all grounds had less than 0.2V drop under load, we determined the internal microprocessor was faulty. Replaced the PCI with part number 2298833 and performed a software flash using DAVIE4 to match the VIN and performance parameters. Total cost for the module was $2,450 plus 3 hours of labor for programming and testing.

Carlos Diaz · Answer

Try a full capacitive discharge. Disconnect both battery cables and hold them together for 30 seconds to drain the capacitors in the modules, then let it sit for 10 minutes before reconnecting. Occasionally this resets the internal watchdog timer on these MX-13 controllers.

Kevin Tran · Answer

I've seen this happen when the charging system is overvolting. Check your alternator output; if it's spiking above 15.5V, it can scramble the microprocessor's logic. If the voltage is steady, you might be looking at a bricked PCI.

Tom Patel · Answer

Before condemning the ECU, make sure you check the grounds on the starter stud and the frame rail. PACCAR modules are extremely sensitive to voltage drops, and a bad ground can trigger internal logic errors that look like a hardware failure.

2021 Peterbilt 579 - PACCAR MX-13 - P0606 FMI 1 ECU Internal Error

Suggest a repair