What Does P0629 Mean?
The PCM has detected a high voltage condition in the fuel pump 'A' control circuit. The circuit is showing voltage above the normal operating range, which may indicate a short to battery voltage. This can lead to uncontrolled fuel pump operation and potential fuel pressure regulation issues.
Safety Warning
An uncontrolled fuel pump can cause excessive fuel pressure and fire risk. The pump may also run with the key off, draining the battery and creating a hazard. Do not drive.
Common Causes
40%
Short to battery voltage in the fuel pump control circuit wiring
25%
Faulty fuel pump relay stuck closed or welded contacts
20%
Failed fuel pump driver module with high output
15%
PCM internal driver failure
Diagnostic Steps
1
Step 1: Remove the fuel pump relay and check if the fuel pump still runs — if yes, the relay contacts are welded shut. Replace the relay.
2
Step 2: With the relay removed, measure voltage on the PCM control terminal in the relay socket — should be near 0V with key on. If battery voltage is present, the wire is shorted to B+.
3
Step 3: Trace the fuel pump control wire from the relay socket to the PCM, inspecting for spots where it may contact a power wire or terminal.
4
Step 4: Disconnect the PCM and recheck for voltage on the control wire — if voltage is still present, the short is in the harness. If gone, suspect PCM.
5
Step 5: Repair wiring short or replace the faulty component as determined by testing.
Estimated Repair Cost
$50 - $600
Parts + labor, varies by vehicle and location
The PCM has detected a high voltage condition in the fuel pump 'A' control circuit. The circuit is showing voltage above the normal operating range, which may indicate a short to battery voltage. This can lead to uncontrolled fuel pump operation and potential fuel pressure regulation issues.
The most common cause of P0629 (Fuel Pump "A" Control Circuit High) is: Short to battery voltage in the fuel pump control circuit wiring
Typical repair costs for P0629 range from $50 to $600, depending on the vehicle, location, and whether you do it yourself or go to a shop.
An uncontrolled fuel pump can cause excessive fuel pressure and fire risk. The pump may also run with the key off, draining the battery and creating a hazard. Do not drive.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0629 to identify the root cause.
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Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
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