P1802

What it means

P1802 is a manufacturer-specific code, and for this entry it is defined as a short circuit to battery voltage in the transmission clutch interlock safety switch circuit. The control unit saw a voltage on the switch signal line that was higher than expected for the switch position, suggesting the circuit is shorted to a power supply. Exact wiring, switch location and strategy vary by make and model, so confirm the details for the specific vehicle.

Symptoms

• Engine will not crank, or cranks only with the clutch pedal pressed in an unusual way
• Engine cranks without the clutch pressed, or starts inconsistently
• Malfunction indicator lamp or transmission warning lamp on
• Cruise control or stop-start function unavailable
• Erratic or limited gear selection on automated manual or similar transmissions

Possible causes

• Clutch interlock switch signal wire shorted to a battery positive feedlikely
• Damaged, chafed or pinched wiring in the harness near the pedal box or bulkheadlikely
• Faulty or internally shorted clutch pedal interlock switchpossible
• Corroded, wet or damaged connector terminals causing a cross-circuit to a power supplypossible
• Aftermarket alarm, remote start or immobiliser wiring interfering with the switch circuitpossible
• Fault inside the control unit that reads the switchrare

How to diagnose

1. Read all stored and pending codes and record the freeze frame data, noting whether other starter, clutch or body control faults are present
2. Check the live data for the clutch switch status and see whether it changes correctly when the pedal is pressed and released
3. Visually inspect the switch, its connector and the surrounding harness for damage, chafing, moisture or corrosion
4. Look for any aftermarket electrical equipment tied into the starter or clutch circuit
5. With the ignition off and the connector unplugged, check the signal wire for unwanted voltage and for continuity to a power feed, following the manufacturer wiring diagram
6. Check the switch itself for correct operation and resistance or continuity in both pedal positions against specification
7. Check the switch adjustment and pedal position where the model allows it
8. If wiring and switch are sound, check the control unit power, earths and signal input before suspecting the unit

How to fix

• Repair or replace the shorted or damaged section of wiring and secure it clear of sharp edges
• Replace the clutch interlock switch if it is faulty or incorrectly adjusted
• Clean or replace corroded connector terminals and ensure the connector seals properly
• Remove or correct faulty aftermarket wiring connected to the circuit
• Replace or repair the control unit only after the wiring and switch are proven good, following manufacturer procedure

Can I keep driving?

Nearby codes

• P1801OtherTransmission Clutch Interlock Safety Switch Open Circuit
• P1803OtherTransmission Clutch Interlock Safety Switch Short Circuit To Ground