What it means
Same as P0635 with the control line shorted to supply. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
The power steering control circuit carries a command used to request steering support or, on some vehicles, raise engine idle under steering load. P0637 sets when the monitored control line reads higher than expected, often because it is shorted to a supply voltage. The high circuit reading does not by itself prove that the steering pump is producing excessive output.
Common causes
Most likely first.
- Control line shorted to supply
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Possible limp mode or no-start
- Multiple follow-up faults across modules
- Reset/relearn may be needed after repair
How to diagnose it
- Save freeze-frame data and scan the steering and engine modules for related faults, noting when the control circuit was reported high.
- Inspect the power steering control harness for pinching or chafing against a battery feed or other supply wire.
- Check the connector for moisture, corrosion, loose contacts, or a pushed-back terminal that could bridge the control line to supply.
- Using the manufacturer’s wiring diagram, test the control line for an unintended connection to a power supply, with the circuit isolated as specified.
- If no wiring short is found, check the steering system’s response to a commanded request and verify the control output before considering module failure.
Common fixes
- Correct a loose or contaminated connector and restore its seal.
- Repair pinched or chafed wiring that has contacted a supply source.
- Replace a damaged connector terminal that is bridging the control circuit.
- Repair a confirmed faulty steering control output or steering-system component.
Can I keep driving?
If steering assistance remains normal, keep driving limited while arranging diagnosis and watch for unexpected changes in steering effort. Stop if assistance becomes erratic or is lost, since the vehicle may be difficult to steer at low speeds.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.