What Does P1803 Mean?
DTC P1803 indicates the clutch interlock safety switch circuit has a short to ground. The PCM sees a constant low signal on the switch input, which typically represents the clutch-not-pressed state. This may prevent the vehicle from starting even with the clutch pedal fully depressed.
Common Causes
35%
Signal wire chafed and grounding against the chassis or pedal bracket
25%
Corroded connector allowing ground path through moisture
20%
Internally shorted clutch switch grounding the signal
10%
Damaged wire insulation in the harness near the firewall pass-through
10%
PCM internal ground fault on the input
Diagnostic Steps
1
Disconnect the clutch switch connector and check if the signal wire shows continuity to ground at the PCM connector; it should show open (infinite resistance).
2
If the short to ground persists with the switch disconnected, trace the wiring from the connector to the PCM, inspecting for bare wire contacting metal.
3
Pay special attention to the firewall grommet area where wires pass through, as this is a common chafe point.
4
Test the switch independently with an ohmmeter for proper operation and no internal short to its mounting (ground).
5
Inspect the connector for green corrosion or moisture intrusion that could create a ground path.
Estimated Repair Cost
$40 - $300
Parts + labor, varies by vehicle and location
DTC P1803 indicates the clutch interlock safety switch circuit has a short to ground. The PCM sees a constant low signal on the switch input, which typically represents the clutch-not-pressed state. This may prevent the vehicle from starting even with the clutch pedal fully depressed.
The most common cause of P1803 (Transmission Clutch Interlock Safety Switch Short Circuit To Ground) is: Signal wire chafed and grounding against the chassis or pedal bracket
Typical repair costs for P1803 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 typically creates a no-start condition as a fail-safe, but intermittent shorts could cause unpredictable starting behavior.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P1803 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Starting System / Transmission
Difficulty
Type
Manufacturer
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
