Auto Shift Manual Mode Circuit Range/Performance
The P0956 code indicates that the Powertrain Control Module (PCM) has detected an issue with the manual shift mode circuit in an automatic transmission. This circuit allows the driver to manually select gears. The PCM monitors voltage and resistance in the circuit; when these values fall outside the expected range or performance parameters, the code is set. This can be caused by a faulty shift selector switch, wiring issues, or a malfunctioning PCM.
1. Symptoms You Will Notice
- Inability to shift manually using the manual mode
- Transmission stuck in a single gear
- Check Engine Light illuminated
- Reduced fuel economy
2. Most Common Causes
- Faulty or worn manual shift mode switch (paddles/selector)
- Short to ground, short to power, or open circuit in the wiring or connectors
- Loose, corroded, or damaged connections in the selector harness
- Internal failure of the Transmission Control Module (TCM)
- Mechanical misalignment of the gear selector
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.
Step 2: Visually inspect the shift selector switch and wiring for damage or corrosion.
Step 3: Test the manual mode switch resistance and voltage with a multimeter and compare to manufacturer specs.
Step 4: Check for continuity in the circuit between the switch and PCM.
Step 5: If all else is fine, test the PCM or have it reprogrammed.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive with this code as it may cause unpredictable shifting or loss of manual mode control, potentially leading to unsafe driving conditions.
How much does it cost to fix?▼
The cost to fix P0956 typically ranges from $50 to $150 for diagnostic and minor repairs like switch replacement, but could be higher if the PCM needs replacement.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.