CEM Communication Lost
The PACCAR-P1613 (PACCAR MX) diesel fault code means: CEM Communication Lost. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- advanced
- Estimated cost
- $800-$6,000
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Common Symptoms
- DPF or DEF warning light
- Engine derate (5 mph, 25% power, then forced shutdown)
- Excessive DEF consumption or dosing fault
- Parked regen required
- High EGT / visible smoke during regen
Probable Causes (Ranked by Likelihood)
- DPF plugged with soot or ash exceeding service threshold Likely
- Failed EGT or differential pressure sensor Likely
- Crystallized or low DEF causing SCR efficiency loss Possible
- Upstream combustion fault (injector, EGR) preventing proper regen Possible
- Short-haul duty cycle preventing passive regen Possible
Step-by-Step Diagnostic Procedure
Pull freeze frame with DAVIE4 and note EGT readings, soot load, and DEF dosing state at fault.
Inspect aftertreatment plumbing for damaged clamps, exhaust leaks, or wiring damage at sensor connectors.
If soot load over 100%, attempt parked regen. Document temperatures — outlet should exceed 1000 F for 20+ minutes.
Check DEF quality with refractometer; replace if concentration drifts below 30% urea.
If NOx efficiency fault persists after sensors and doser verified, SCR catalyst may need replacement.
Frequently Asked Questions
What does PACCAR MX code P1613 mean?
PACCAR MX code P1613 (CEM Communication Lost) 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 aftertreatment system that should be diagnosed with DAVIE4 or PACCAR ESA.
Can I drive a Kenworth or Peterbilt with PACCAR P1613?
Possibly — short distances may be OK, but ignoring the fault risks progressive damage, regen failure, or derate. Address promptly.
How much does it cost to fix PACCAR MX P1613?
Typical repair runs $800-$6,000. 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.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P1613 on Other Platforms
The same code ID appears across other engines, vehicles, and equipment. Diagnostic flow varies by platform — see the matching breakdown: