What Does P0704 Mean?
The TCM has detected a malfunction in the clutch switch input circuit (on manual transmission vehicles) or the brake switch B circuit (context-dependent by manufacturer). This switch tells the TCM whether the clutch pedal is depressed, which affects starting interlock, shift point adaptation, and fuel cutoff logic. The driver may notice the vehicle not starting (clutch interlock failure), incorrect shift point adaptation, or a check engine light.
Common Causes
40%
Faulty clutch pedal position switch — stuck, worn contacts, or out of adjustment
25%
Wiring fault in the clutch switch circuit — open, short, or high resistance
15%
Corroded or damaged clutch switch connector pins
12%
Clutch switch misadjusted or mounting clip broken after pedal service
8%
ECM/TCM internal fault in the clutch switch input circuit
Diagnostic Steps
1
Monitor the clutch switch signal on the scan tool while pressing and releasing the clutch pedal — the signal should toggle cleanly between engaged and disengaged without erratic behavior.
2
Locate the clutch pedal switch at the top of the clutch pedal arm and test continuity with a multimeter while pressing/releasing the pedal. The switch should open/close cleanly.
3
Inspect the switch mounting — many clutch switches use a plastic self-adjusting clip that can break or fall off, preventing proper switch actuation.
4
Check the wiring from the clutch switch to the ECM/TCM, focusing on the routing through the firewall grommet and under-dash area where wires can be pinched or chafed.
5
Verify the clutch start interlock function — the engine should only crank with the clutch pedal fully depressed. If it cranks without the clutch, the switch circuit is bypassed or shorted.
Estimated Repair Cost
$25 - $175
Parts + labor, varies by vehicle and location
The TCM has detected a malfunction in the clutch switch input circuit (on manual transmission vehicles) or the brake switch B circuit (context-dependent by manufacturer). This switch tells the TCM whether the clutch pedal is depressed, which affects starting interlock, shift point adaptation, and fu...
The most common cause of P0704 (Torque Converter/Brake Switch B Circuit Malfunction) is: Faulty clutch pedal position switch — stuck, worn contacts, or out of adjustment
Typical repair costs for P0704 range from $25 to $175, depending on the vehicle, location, and whether you do it yourself or go to a shop.
A faulty clutch switch can disable the clutch start interlock, allowing the engine to crank in gear (potential rollaway hazard). It can also affect shift point adaptation and fuel cutoff logic. If the vehicle can start without the clutch depressed, treat this as a safety concern and address it immediately.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0704 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Control System / Clutch Input
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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