AutoCodes – Generic – P2500

P2500 Code - Low Signal Voltage On Generator Turn ON Signal Circuit

Quick Answer

The Engine Control Module (ECM) uses the generator turn ON signal circuit to control the load of the generator on the engine. Common causes include Faulty Generator (Alternator), Generator harness is open or shorted, Generator 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: P2500 indicates Low Signal Voltage On Generator Turn ON Signal Circuit.
Common causes: Common causes include Faulty Generator (Alternator), Generator harness is open or shorted, Generator 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 20,798

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 Sep 01, 2020

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P2500 Description

The Engine Control Module (ECM) uses the generator turn ON signal circuit to control the load of the generator on the engine. A high-side driver in the ECM applies a voltage to the voltage regulator. This signals the voltage regulator to turn the field circuit ON and OFF. When ECM turns ON the high-side driver, the voltage regulator turns ON the field circuit. When ECM turns OFF the high-side driver, the voltage regulator turns OFF the field circuit.
The ECM monitors the state of the generator turn ON signal circuit. With the engine running, ECM should detect a high generator turn ON signal circuit. The Diagnostic Trouble Code (DTC) will set when the ECM detects a low signal voltage on the generator turn ON signal circuit for at least 15 seconds.

OBDII Code P2500 - Low Signal Voltage On Generator Turn ON Signal Circuit - AutoCodes.com — P2500 Code - Low Signal Voltage On Generator Turn ON Signal Circuit

What does this mean?

What are the Possible Causes of the DTC P2500?

Faulty Generator (Alternator)
Generator harness is open or shorted
Generator circuit poor electrical connection
Faulty Engine Control Module (ECM)

How to Fix the DTC P2500?

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 is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P2500 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.

Need more information about the P2500 code?

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Information for Specific Makes

P2500 Buick — Low Signal Voltage On Generator Turn ON Signal Circuit
P2500 Cadillac — Low Signal Voltage On Generator Turn ON Signal Circuit
P2500 Chevrolet — Low Signal Voltage On Generator Turn ON Signal Circuit
P2500 Dodge — Low Signal Voltage On Generator Turn ON Signal Circuit
P2500 GMC — Low Signal Voltage On Generator Turn ON Signal Circuit

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.