Technical Diagnostic Reference

COMS Error - IPM Board Resistor Check

How to confirm a faulty resistor using a multimeter in diode test mode
A communication error (COMS error) may occur due to a faulty resistor on the IPM (Intelligent Power Module) board. Use the following test to confirm the resistor condition.

Diagnostic procedure

1
Set the multimeter to diode test mode.
2
Measure across the suspect resistor.
  • In one direction, the reading should be approximately 0.45 V (diode forward voltage).
  • Reverse the meter leads. The reading should be approximately 1.1 V.

Diagnosis

Meter resultAssessmentRequired action
Approximately 0.45 V in one direction and 1.1 V with the leads reversedExpected readingsContinue diagnosis as required.
O/L, open loop or open circuit in both directionsResistor is faultyReplace the resistor.
Fault confirmed: An open-circuit reading in both directions confirms that the resistor is faulty and must be replaced.

Reference image

IPM board resistor diagnostic reference