AutoCodes – Cadillac – P0651 Cadillac

P0651 Cadillac Code - 5 Volt Reference 2 Circuit

Quick Answer

The Engine Control Module (ECM) has four (4) internal 5 Volt reference circuits (Some models have two (2) internal 5 Volt reference circuits). Common causes include Faulty Sensor on 5 Volt circuit, Sensor on 5 Volt circuit harness is open or shorted, Sensor on 5 Volt circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

What it means: P0651 Cadillac indicates 5 Volt Reference 2 Circuit.
Common causes: Common causes include Faulty Sensor on 5 Volt circuit, Sensor on 5 Volt circuit harness is open or shorted, Sensor on 5 Volt circuit poor electrical connection.
Severity: High - diagnose this code as soon as possible.
Can I drive?: Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.

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Code Popularity 13,401

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Jul 17, 2022

Description
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P0651 Cadillac Description

The Engine Control Module (ECM) has four (4) internal 5 Volt reference circuits (Some models have two (2) internal 5 Volt reference circuits). Each internal reference circuit provides external 5 Volt reference circuits for more than one sensor. A short to ground or short to voltage on one external 5 Volt reference circuit can affect all the components connected to the same internal 5 Volt reference circuit. The Diagnostic Trouble Code (DTC) will be set when the ECM detects a short to voltage or ground on any of the 5 Volt reference circuits for greater than 0.5 s.

OBDII Code P0651 Cadillac - 5 Volt Reference 2 Circuit - AutoCodes.com — P0651 Cadillac Code - 5 Volt Reference 2 Circuit

What does this mean?

What are the Possible Causes of the DTC P0651 Cadillac?

Faulty Sensor on 5 Volt circuit
Sensor on 5 Volt circuit harness is open or shorted
Sensor on 5 Volt circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P0651 Cadillac?

Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.

What does this mean?

Code Tech Notes

Disconnecting one component at a time from the affected 5 Volt reference circuit while observing the scan tool 5 Volt Reference Circuit Status parameter may help locate the fault. The scan tool parameter will change from Malfunction to OK when the source of the fault is disconnected. If all 5 Volt reference components have been disconnected and a fault is still indicated, the fault may exist in the wiring harness.

The 5 Volt reference 2 circuit provides 5 Volt to the following sensors: (Some models may have different sensors, please consult the factory service manual for the list of sensors for your model and year)

- Brake pedal position sensor
- Crankshaft position sensor

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0651 Cadillac code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.

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About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.