Applicable Systems
OBD-II
Symptoms
The check engine light illuminates. The transmission may not shift correctly, may slip, or enter limp-home mode. A transmission control system component has a malfunction.
Possible Causes
- Faulty pressure control solenoid
- Transmission fluid temperature sensor fault
- TCC (torque converter clutch) solenoid circuit fault
- Transmission internal mechanical fault
- Wiring harness damage to transmission connector
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 wiring and connectors for the indicated system
Wiring and connectors are in good condition - Step 3: Use a digital multimeter to check sensor voltage, resistance, and continuity per manufacturer specifications
Values are within specified range - Step 4: Test the related actuator, sensor, or solenoid for proper operation
Component operates within specification or fails definitively - Step 5: Clear codes and perform a road test or drive cycle to verify repair
Code does not return and system operates normally
How to Reset
To reset code P0851: 1) Repair the underlying fault. 2) Use an OBD-II scan tool to clear the DTC. 3) Perform a drive cycle to verify the monitor completes. 4) If the code returns, further diagnosis is needed. Caution: Do not clear codes without fixing the root cause.
Frequently Asked Questions
- Q: What does OBD-II code P0851 mean?
Code P0851 indicates: Transmission Control - Code 851. This is a SAE J2012 standard diagnostic trouble code related to Transmission Control.
- Q: How serious is code P0851?
Severity: Major. Immediate attention is recommended.
- Q: Can I drive with code P0851?
Not recommended - may cause further damage.
- Q: How do I fix code P0851?
Diagnose the Transmission Control system, check wiring and connectors, test related components, and replace faulty parts as needed.
Source: SAE J2012 Standard - Powertrain Diagnostic Trouble Codes
Category: OBD-II