Applicable Systems
OBD-II
Symptoms
The ECM has lost communication with the transmission control module.
Possible Causes
- CAN bus wiring fault between ECM and TCM
- TCM power or ground fault
- TCM internal fault
- CAN bus termination resistor fault
- EMI interfering with CAN bus
Troubleshooting Steps
- Step 1: Connect an OBD-II scan tool and read all stored DTCs and freeze frame data
All DTCs and freeze frame data are retrieved - Step 2: Inspect the related sensor or actuator wiring for damage, corrosion, or loose connections
Wiring and connectors are in good condition - Step 3: Use a digital multimeter to check sensor voltage, resistance, and reference signals per manufacturer specifications
Values are within specified range - Step 4: Perform component-level testing of the suspected sensor or actuator
Component passes or fails definitively - Step 5: Clear codes and road test to verify repair
Code does not return and system operates normally
How to Reset
To reset code P1612: 1) Repair the underlying fault. 2) Use an OBD-II scan tool to clear the DTC. 3) Perform a drive cycle.
Frequently Asked Questions
- Q: What does OBD-II code P1612 mean?
Code P1612 indicates: Transmission Control Module Communication Fault. This is a Mercedes-Benz manufacturer-specific diagnostic trouble code.
- Q: Is code P1612 serious?
Severity: Major. Service as needed.
- Q: How do I fix code P1612?
Diagnose the Communication system and replace faulty components.
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Source: OBD-II Manufacturer Extended Codes / SAE J2012 / OBD-Codes.com
Category: OBD-II
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