Engine ECM Software Calibration Incompatibility
The PACCAR-P1004 (PACCAR MX) diesel fault code means: Engine ECM Software Calibration Incompatibility. This is a serious severity code.
- Keep driving?
- No — stop driving
- DIY difficulty
- advanced
- Estimated cost
- $1,800-$4,500
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Common Symptoms
- Check Engine Light illuminated
- Possible no-start or stalling
- Scan tool communication loss
- Engine derate or limp mode
Probable Causes (Ranked by Likelihood)
- ECM internal hardware fault Likely
- Software corruption requiring reflash Likely
- Power or ground circuit issue Possible
- Low battery voltage during key-on Possible
Frequently Asked Questions
What does PACCAR MX code P1004 mean?
PACCAR MX code P1004 (Engine ECM Software Calibration Incompatibility) is a serious-severity diagnostic trouble code set by the engine or aftertreatment control module on MX-11 and MX-13 engines in Kenworth and Peterbilt trucks. It indicates a fault in the engine control system that should be diagnosed with DAVIE4 or PACCAR ESA.
Can I drive a Kenworth or Peterbilt with PACCAR P1004?
No — this fault typically triggers engine derate or forced shutdown countdown. Continuing to operate risks further damage or a stranded truck.
How much does it cost to fix PACCAR MX P1004?
Typical repair runs $1,800-$4,500. Sensor or wiring repairs are at the low end; injector, DEF pump, DPF, or EGR cooler jobs are at the high end. Dealer-level DAVIE4 software is often required for programming or calibration after parts replacement.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
Connect DAVIE4 or PACCAR ESA and confirm P1004 is active with freeze frame data.
Measure ECM supply voltage at pin — must be battery voltage key-on and stable during cranking.
Inspect ECM grounds at frame rail for clean, corrosion-free connections.
Check for PACCAR calibration updates and reflash if available.
If fault persists after reflash and wiring checks, ECM replacement with DAVIE4 programming is required.
Sources 1
This page is built from documented references. Verify against your own service info before repair work.
- SAE J1939-73Application Layer: Diagnostics (defines the SPN/FMI fault-identifier framework)
P1004 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown:
Commonly Affected Vehicles
- Kenworth T680 with PACCAR MX-13
- Kenworth T880 with PACCAR MX-13
- Kenworth W990 with PACCAR MX-13
- Peterbilt 579 with PACCAR MX-13
- Peterbilt 389 with PACCAR MX-13
- Peterbilt 567 with PACCAR MX-13
- Kenworth T440 with PACCAR MX-11
- Kenworth T470 with PACCAR MX-11
- Peterbilt 520 with PACCAR MX-11
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