Engine Camshaft Position Signal Abnormal
The VOLVO-MACK-MID128-PID723-FMI8 (Volvo/Mack D/MP Series) diesel fault code means: Engine Camshaft Position Signal Abnormal. This is a serious severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- intermediate
- Estimated cost
- $300-$1,800
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Common Symptoms
- Rough running or extended crank time
- Engine may run on CKP backup only (reduced power)
- Check Engine Light illuminated
- Possible misfire code on specific cylinders
- Engine derate
Probable Causes (Ranked by Likelihood)
- Failed camshaft position sensor Very Likely
- Damaged camshaft tone wheel or worn key Possible
- Wiring harness damage near valve cover Likely
- Loose sensor mounting causing excessive air gap Possible
- ECM input circuit fault Less Likely
Step-by-Step Diagnostic Procedure
Connect Volvo PTT or Mack Guided Diagnostics and monitor CMP signal live; compare to CKP for cam/crank correlation.
Measure CMP sensor resistance and supply voltage at the sensor connector.
Inspect sensor mounting bolts for correct torque and check tip for debris.
Back-probe and capture CMP signal waveform with oscilloscope during cranking.
Inspect harness routing on valve cover for heat damage or chafe.
If sensor and harness test good, verify timing gear and key are intact on the camshaft.
Frequently Asked Questions
What does Volvo/Mack code MID128-PID723-FMI8 mean?
Volvo/Mack code MID128-PID723-FMI8 (Engine Camshaft Position Signal Abnormal) is a serious-severity diagnostic trouble code set on D11/MP7, D13/MP8, and D16/MP10 diesel engines in Volvo VNL/VNR and Mack Anthem/Pinnacle/Granite/Titan trucks. It indicates a fault in the CMP sensor system and should be read with Volvo Premium Tech Tool (PTT) or Mack Guided Diagnostics.
Can I drive a Volvo or Mack truck with code MID128-PID723-FMI8?
Short distances may be acceptable to reach a repair facility, but the fault will escalate to derate (typically 55 mph then 5 mph on aftertreatment faults). Do not defer diagnosis beyond a shift.
How much does it cost to fix Volvo/Mack code MID128-PID723-FMI8?
Typical repair falls in the range $300-$1,800. Sensor/wiring repairs are at the low end; EGR cooler, NOx sensor set, DEF pump, injector, or head work runs at the high end. Volvo PTT or Mack Guided Diagnostics is normally required for calibration and parameter programming.