P0858
PowertrainTransmissionmoderate severityTCM Communication Circuit Range/Performance
What P0858 Means
The signal from the Transmission Control Module communication circuit is outside the expected range. This can disrupt data exchange between the TCM and other modules.
Symptoms
- Transmission warning light on
- Erratic shifting
- Communication fault codes
Common Causes
- Faulty wiring or connectors
- Poor ground connection
- Failed TCM
- Damaged communication bus
Diagnostic Steps
- Scan for related communication codes
- Inspect TCM wiring and connectors
- Check circuit for shorts and opens
- Test TCM signal voltage
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