P1631: Theft Deterrent Start Enable Signal Not Correct/ Main Relay Malfunction (Power Hold)

OTHER VOLKSWAGEN BUICK CADILLAC CHEVY GM GMC OLDSMOBILE

Severity

Medium

System

Manufacturer-Specific Powertrain

Last reviewed: Jan 1, 0001 Last updated: Jan 1, 0001

Methodology: We combine code standards with complaint and reliability patterns, then review for clear, vehicle-first diagnosis steps.

Sources: SAE/OBD-II definitions, manufacturer service information, and public reliability reports (including NHTSA where applicable).

Limits: Guidance is informational and may not match every model-year or revision. Confirm with the official manual and diagnostics before replacing parts. For safety-critical or electrical work, use a qualified technician.

What Does P1631 Mean?

P1631 is a manufacturer-specific diagnostic trouble code: Theft Deterrent Start Enable Signal Not Correct/ Main Relay Malfunction (Power Hold). This code applies to OTHER, VOLKSWAGEN, BUICK, CADILLAC, CHEVY vehicles. Unlike generic OBD-II codes, manufacturer-specific codes are defined by the vehicle maker and may only apply to certain makes and models.

Symptoms of P1631

⚠️ Check Engine Light (MIL) illuminated
⚠️ Theft Deterrent Start Enable Signal Not Correct/ Main Relay not operating correctly
⚠️ Related system in reduced functionality mode
⚠️ Reduced engine performance

Common Causes

🔍 Theft Deterrent Start Enable Signal Not Correct/ Main Relay has failed or is degraded
🔍 Wiring or connector issue in Theft Deterrent Start Enable Signal Not Correct/ Main Relay circuit
🔍 Related mechanical component affecting Theft Deterrent Start Enable Signal Not Correct/ Main Relay
🔍 Software update needed for ECM/PCM

Frequently Asked Questions

What does P1631 mean?

P1631 indicates: Theft Deterrent Start Enable Signal Not Correct/ Main Relay Malfunction (Power Hold). The vehicle's computer has detected that the Theft Deterrent Start Enable Signal Not Correct/ Main Relay is not operating within its expected parameters and stored this diagnostic trouble code.

Can I drive with code P1631?

You can drive short distances for essential trips, but schedule a diagnosis soon. Driving with P1631 for extended periods may cause additional problems.

How much does it cost to fix P1631?

Repair costs for P1631 typically range from $80 to $300, depending on the root cause. Simple wiring or connector repairs are on the lower end, while component replacement costs more. A proper diagnosis ($80–$150 at most shops) will identify the exact cause before committing to expensive parts.

What To Do Next

Possible Fixes

🔧 Inspect Theft Deterrent Start Enable Signal Not Correct/ Main Relay and related wiring
🔧 Replace faulty Theft Deterrent Start Enable Signal Not Correct/ Main Relay

1
Find your vehicle above
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2
Check for recalls
Go to nhtsa.gov/recalls and enter your VIN. Free repairs if covered.
3
Get a professional diagnosis
A code alone doesn't identify the exact failed part. A diagnostic ($50–$150) pinpoints the root cause.