Cummins ISB CM850 (2003-06) Fault Code: 528 PID: 93 SPN: 93 FMI: 2 Auxiliary Alternate Torque Validation Switch – Data Erratic, Intermittent, or Incorrect. An error has been detected in the alternate torque switch circuit.

Posted by PerDiezel Solutions on January 18, 2026

The switch can be monitored for proper operation in INSITE? electronic service tool. If the switch is changing state correctly on the service tool, then the problem does not lie in the switch circuit.

The three position-switch has three states:

1)Position 1 – open
2)Position 2 – closed
3)Position 3 – 1500 ohm resistance

The two position-switch has two states:

1)Position 1 – open
2)Position 2 – closed

Possible repairs:

1)Replace the alternate torque switch.
2)Repair or replace the OEM harness.
3)The removal and reinstallation of the connector may correct the fault.

Cummins ISB CM850 (2003-06) Fault Code: 527 PID: SID 154 SPN: 702 FMI: 3 Auxiliary Input/Output 2 Circuit Voltage Above Normal or Shorted to High Source. High signal voltage or open circuit has been detected at the auxiliary input and output 2 circuit.

Cummins ISB CM850 (2003-06) Fault Code: 523 PID: 89 SPN: 611 FMI: 2 Auxiliary Intermediate (PTO) Speed Switch Validation – Data Erratic, Intermittent, or Incorrect. The position of the intermediate speed control switch 1 does not match the position of the intermediate speed control validation switch.

Cummins ISB CM850 (2003-06) Fault Code: 499 PID: 98 SPN: 98 FMI: 4 Engine Oil Level Sensor Circuit – Voltage Below Normal or Shorted to Low Source. The engine oil level sensor has detected an internal failure.

Cummins ISB CM850 (2003-06) Fault Code: 498 PID: 98 SPN: 98 FMI: 3 Engine Oil Level Sensor Circuit – Voltage Above Normal or Shorted to High Source. The engine oil level sensor has detected an internal failure.

Cummins ISB CM850 (2003-06) Fault Code: 497 PID: SID 114 SPN: 1137 FMI: 2 Multiple Unit Synchronization Switch – Data Erratic, Intermittent, or Incorrect. Multi-Unit synchronous ON/OFF switch and Multi-Unit synchronous complimentary ON/OFF switch have different values in the ECM.

Cummins ISB CM850 (2003-06) Fault Code: 488 PID: 105 SPN: 105 FMI: 0 Intake Manifold 1 Temperature – Data Valid but Above Normal Operational Range – Moderately Severe Level. Intake manifold air temperature signal indicates intake manifold air temperature above engine protection warning limit.

WARNING!