Transmission Mode Switch Circuit Low
The P071B code indicates that the Powertrain Control Module (PCM) has detected a low voltage condition in the transmission mode switch circuit. This switch, often part of the manual shift or sport mode system, sends a signal to the PCM to select different shift patterns. A low circuit condition can be caused by a faulty switch, damaged wiring, or a poor electrical connection, leading to incorrect transmission operation.
01. Most Common Causes
- Faulty transmission mode switch
- Damaged or corroded wiring/connectors in the switch circuit
- Short to ground in the switch circuit
- Faulty PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Transmission stuck in a single mode (e.g., only sport mode)
- Erratic shifting or harsh engagement
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for related codes.
Step 2: Visually inspect the transmission mode switch and its wiring for damage, corrosion, or loose connections.
Step 3: Test the switch resistance and voltage with a multimeter; compare to manufacturer specs.
Step 4: If switch and wiring are okay, check for a short to ground in the circuit; repair as needed.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended. Driving with a low circuit condition can cause unpredictable transmission behavior, potentially leading to unsafe driving conditions or further transmission damage.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150 for diagnosis and repair, depending on whether the switch needs replacement or wiring repair.