AutoCodes – Generic – P2603

P2603 Code - Coolant Pump 'A' Control Circuit High

Quick Answer

The Powertrain Control Module (PCM) monitors the Coolant Pump 'A' Control Circuit signal. Common causes include Faulty Coolant Pump Relay, Faulty Coolant Pump, Coolant Pump harness is open or shorted. 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: P2603 indicates Coolant Pump 'A' Control Circuit High.
Common causes: Common causes include Faulty Coolant Pump Relay, Faulty Coolant Pump, Coolant Pump harness is open or shorted.
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 13,537

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 Jan 19, 2019

Description
Possible Causes
How To Fix
Cost to Diagnose
Comments
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Code P2603 Description

The Powertrain Control Module (PCM) monitors the Coolant Pump 'A' Control Circuit signal. The PCM sets the OBDII code when the Coolant Pump 'A' Control Circuit signal is out of factory specifications.

OBDII Code P2603 - Coolant Pump 'A' Control Circuit High - AutoCodes.com — P2603 Code - Coolant Pump 'A' Control Circuit High

What does this mean?

What are the Possible Causes of the DTC P2603?

Faulty Coolant Pump Relay
Faulty Coolant Pump
Coolant Pump harness is open or shorted
Coolant Pump poor electrical connection

How to Fix the DTC P2603?

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 P2603 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 P2603 code?

Need more information on how to fix the P2603 code? Get Access to Factory Service Manuals

Need Help with the Code?

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Information for Specific Makes

P2603 Buick — Auxiliary Coolant Pump Circuit High
P2603 Cadillac — Auxiliary Coolant Pump Circuit High
P2603 Chevrolet — Auxiliary Coolant Pump Circuit High
P2603 Dodge — Coolant Pump 'A' Control Circuit High
P2603 GMC — Auxiliary Coolant Pump Circuit High

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.