P0899
PowertrainTransmissionmoderate severityTransmission Control System MIL Request Circuit High
What P0899 Means
The transmission control module MIL request circuit is reading higher voltage than expected. This usually points to an open circuit or wiring fault between modules.
Symptoms
- MIL operation abnormal
- Transmission warning light
- Possible limp mode
Common Causes
- Open or high resistance in MIL request circuit
- Faulty transmission control module
- Corroded or loose connectors
- PCM/TCM communication fault
Diagnostic Steps
- Check MIL request circuit for opens or high resistance
- Inspect connectors for corrosion
- Verify communication between PCM and TCM
- Test module supply voltage and grounds
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