Auto Shift Manual Mode Circuit Intermittent
The P0959 code indicates an intermittent fault in the manual shift mode circuit of an automatic transmission. This circuit allows the driver to manually select gears via the shift lever or paddles. An intermittent signal suggests a loose connection, damaged wiring, or a failing transmission control module (TCM). The issue may cause erratic shifting or loss of manual mode functionality.
01. Most Common Causes
- Faulty manual shift mode switch
- Damaged or corroded wiring/connectors in the shift circuit
- Intermittent open or short in the circuit
- Failing transmission control module (TCM)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Inability to shift manually or erratic manual mode operation
- Transmission stuck in automatic mode
- Harsh or delayed shifts when using manual mode
03. Step-by-Step Diagnosis
Step 1: Scan the vehicle for additional codes and freeze frame data.
Step 2: Visually inspect the manual shift mode switch and wiring for damage or corrosion.
Step 3: Test the circuit continuity and resistance using a multimeter.
Step 4: Check for intermittent faults by wiggling harnesses while monitoring the circuit.
Step 5: If necessary, test the TCM for proper operation and update software.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe for short distances, but intermittent loss of manual mode can be distracting. Have it diagnosed soon to avoid potential transmission damage.
How much does it cost to fix?▼
Diagnosis typically costs $50-$150. Repair costs vary: a switch replacement may be $100-$300, while wiring repairs or TCM replacement can be higher.