ABS Wheel Speed Sensor Erratic (Rear Axle)
The VOLVO-MACK-MID136-PID790-FMI2 (Volvo/Mack D/MP Series) diesel fault code means: ABS Wheel Speed Sensor Erratic (Rear Axle). This is a moderate severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- intermediate
- Estimated cost
- $200-$900
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Common Symptoms
- ABS warning lamp illuminated
- Possible ATC (traction control) disabled
- ABS disabled during the affected wheel
- Check Engine Light may also set from multiplexing
Probable Causes (Ranked by Likelihood)
- Failed ABS wheel speed sensor Likely
- Harness damage at wheel end or frame crossover Likely
- Tone ring contaminated with metal debris Possible
- Incorrect sensor air gap from loose mounting Possible
- ABS ECU fault Less Likely
Frequently Asked Questions
What does Volvo/Mack code MID136-PID790-FMI2 mean?
Volvo/Mack code MID136-PID790-FMI2 (ABS Wheel Speed Sensor Erratic (Rear Axle)) is a moderate-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 ABS wheel speed 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 MID136-PID790-FMI2?
Limited short-term operation is usually possible, but the fault will illuminate the Check Engine Light and should be diagnosed promptly to avoid cascading aftertreatment or fueling faults.
How much does it cost to fix Volvo/Mack code MID136-PID790-FMI2?
Typical repair falls in the range $200-$900. 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.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
Connect Volvo PTT or Mack Guided Diagnostics (ABS module) and verify MID136-PID790-FMI2 active; read wheel speed live data.
Inspect sensor mounting and air gap; clean tone ring of metallic debris.
Measure sensor resistance at the harness (spec typically 1000-2500 ohms).
Inspect harness routing for chafe at axle flex point and frame crossover.
After repair, road-test above 5 mph to verify fault clears and ABS lamp goes out.
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)
Commonly Affected Vehicles
- Volvo VNL 760/860 with D13
- Volvo VNR 640 with D11/D13
- Mack Anthem with MP8
- Mack Pinnacle with MP7/MP8
- Mack Granite with MP7/MP8
- Mack Titan with MP10
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