P0637 code meaning
Power Steering Control Circuit High
What P0637 means
P0635–P0637 concern the control or signal circuit between engine module and power steering – depending on the maker the drive of an electro-hydraulic pump or the steering load signal the engine module uses to raise idle. CARB requires power steering components to be monitored only if another diagnostic uses them, so these codes are rare and maker-specific. Mercedes-Benz stores P0635 in the electric steering module itself (no assist after start, software update); no engine module table available to us uses P0635–P0637. P0637 means the voltage in this circuit is too high – a short to battery voltage, or the driver or steering module reports a high state although 'off' was commanded; an electro-hydraulic pump may then keep running. No manufacturer threshold is published.
P0637 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0637
- Power steering warning
- Heavy steering or pump running constantly
- Check engine light possible
Common causes of P0637
- Most likelyControl or signal wire shorted to battery voltage
- PossibleSteering module or pump module faulty internally
- Less likelyOvervoltage from the alternator regulator
- Less likelyEngine module faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Power steering control circuitPower steering moduleEngine control module
What each part of P0637 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 6 | Area: computer (engine control module) and output circuits. |
| 37 | The exact fault in that area. |
What to do next
- Note P0637 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0637
What does P0637 mean?
P0637 means "Power Steering Control Circuit High". P0635–P0637 concern the control or signal circuit between engine module and power steering – depending on the maker the drive of an electro-hydraulic pump or the steering load signal the engine module uses to raise idle. It is a generic code, so it means the same on every make.
Is it safe to drive with P0637?
Drive gently and only to a workshop. With P0637 the car can go into limp mode (reduced power) to protect itself.
Will P0637 fail an emissions test?
P0637 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0637 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will P0637 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.