What Does P1808 Mean?
DTC P1808 indicates the transmission clutch interlock safety switch circuit has a short to ground. The PCM detects that the signal line is pulled low continuously, preventing it from seeing the clutch-pressed state. This typically results in a no-crank condition since the PCM thinks the clutch is never depressed.
Common Causes
35%
Signal wire grounding against the clutch pedal bracket or firewall
25%
Moisture intrusion in the switch connector causing a ground fault
20%
Clutch switch internally shorted to its mounting ground
10%
Damaged insulation where the harness passes through the firewall grommet
10%
PCM input pin shorted internally to ground
Diagnostic Steps
1
Disconnect the clutch interlock switch and measure resistance from the signal wire to ground at the PCM connector; it should read open (no continuity).
2
If the short persists with the switch disconnected, section-test the harness to locate the ground fault.
3
Inspect the wiring carefully around the clutch pedal assembly, firewall pass-through, and any harness clamps for worn insulation.
4
Check the switch connector for moisture, corrosion, or debris that could bridge the signal to ground.
5
Test the switch independently for any internal ground fault by measuring between each terminal and the switch body.
Estimated Repair Cost
$40 - $300
Parts + labor, varies by vehicle and location
DTC P1808 indicates the transmission clutch interlock safety switch circuit has a short to ground. The PCM detects that the signal line is pulled low continuously, preventing it from seeing the clutch-pressed state. This typically results in a no-crank condition since the PCM thinks the clutch is ne...
The most common cause of P1808 (Transmission Clutch Interlock Safety Switch Short Circuit To Ground) is: Signal wire grounding against the clutch pedal bracket or firewall
Typical repair costs for P1808 range from $40 to $300, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A short to ground on this circuit typically prevents starting, which is a fail-safe condition. However, intermittent faults could cause unexpected no-start situations in unsafe locations.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1808 to identify the root cause.
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Quick Info
Category
Powertrain
System
Starting System / Transmission
Difficulty
Type
Manufacturer
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