What Does P0637 Mean?
The PCM has detected a high voltage condition in the power steering control circuit. The signal voltage is above the expected operating range, which may cause the power steering to provide excessive or unpredictable assist levels.
Common Causes
35%
Short to battery voltage in the power steering control circuit wiring
30%
Faulty power steering control module with high output
20%
Open ground circuit at the EPS module causing voltage to float high
15%
PCM internal power steering driver circuit failure
Diagnostic Steps
1
Step 1: Measure voltage on the power steering control signal wire at the PCM connector — compare to specification. Voltage above 5V typically indicates a fault.
2
Step 2: Disconnect the EPS module and recheck the control wire voltage at the PCM — if still high, the wire is shorted to B+ in the harness.
3
Step 3: Verify the EPS module ground circuit — measure resistance from the ground pin to chassis. An open ground will cause the signal to float high.
4
Step 4: Trace the control wire from the PCM to the EPS module, checking for contact with power wires or terminals.
5
Step 5: If wiring and grounds are good, the EPS module or PCM driver is at fault — replace the suspect component.
Estimated Repair Cost
$150 - $1,100
Parts + labor, varies by vehicle and location
The PCM has detected a high voltage condition in the power steering control circuit. The signal voltage is above the expected operating range, which may cause the power steering to provide excessive or unpredictable assist levels.
The most common cause of P0637 (Power Steering Control Circuit High) is: Short to battery voltage in the power steering control circuit wiring
Typical repair costs for P0637 range from $150 to $1,100, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Steering may feel overly sensitive or provide too much assist, making the vehicle feel unstable at highway speeds. Use caution when driving and repair soon.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0637 to identify the root cause.
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Quick Info
Category
Powertrain
System
Power Steering System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
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