AutoCodes – GMC – P2603 GMC

P2603 GMC Code - Auxiliary Coolant Pump Circuit High

Quick Answer

The auxiliary coolant pump and cooling fan system provides a measure of prevention against fuel vaporization due to excessive engine temperatures. Common causes include Faulty Auxiliary Coolant Pump Relay, Blocked pump control passage, Faulty Auxiliary Coolant Pump. 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 GMC indicates Auxiliary Coolant Pump Circuit High.
Common causes: Common causes include Faulty Auxiliary Coolant Pump Relay, Blocked pump control passage, Faulty Auxiliary Coolant Pump.
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 1,425

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
FAQs
Comments
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Code P2603 GMC Description

The auxiliary coolant pump and cooling fan system provides a measure of prevention against fuel vaporization due to excessive engine temperatures. The Engine Control Module (ECM) commands the auxiliary or after boil coolant pump ON when the engine coolant temperature exceeds a calibrated value after engine shut down. The ECM applies ground to the coil side of the auxiliary pump relay. This energizes the coil and applies voltage directly to the pump motor through the switch side of the relay. When the auxiliary coolant pump is activated, coolant is drawn from radiator and pumped into the engine through a tee in the engine coolant inlet pipe. As the colder temperature coolant is drawn into the engine warmer coolant is expelled from the engine and back to the radiator. Removing high temperature coolant from the engine after shut down helps prevent vaporization of the fuel that remains in the fuel injectors and fuel rail during a hot soak.

OBDII Code P2603 GMC - Auxiliary Coolant Pump Circuit High - AutoCodes.com — P2603 GMC Code - Auxiliary Coolant Pump Circuit High

What does this mean?

What are the Possible Causes of the DTC P2603 GMC?

Faulty Auxiliary Coolant Pump Relay
Blocked pump control passage
Faulty Auxiliary Coolant Pump
Auxiliary Coolant Pump harness is open or shorted
Auxiliary Coolant Pump circuit poor electrical connection

How to Fix the DTC P2603 GMC?

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 GMC 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.

Frequently Asked Questions about P2603 GMC Code

1. What are common symptoms of OBDII code P2603 GMC (Auxiliary Coolant Pump Circuit High)?

- Common symptoms include overheating engine, illuminated Check Engine light, and decreased fuel efficiency.

2. What are the possible causes of OBDII code P2603 GMC?

- The code P2603 GMC is typically caused by a faulty auxiliary coolant pump, damaged wiring or connectors, or a malfunctioning powertrain control module (PCM).

3. How can I diagnose the issue related to OBDII code P2603 GMC?

- To diagnose the issue, you can use an OBDII scanner to read the trouble codes, check the auxiliary coolant pump for proper function, inspect the wiring and connectors for damage, and test the PCM for any faults.

4. Are there any DIY repair tips for fixing OBDII code P2603 GMC?

- DIY repair tips include checking and replacing damaged wiring or connectors, testing and replacing the auxiliary coolant pump if necessary, and resetting the fault codes using an OBDII scanner.

5. Can driving with OBDII code P2603 GMC cause further damage to the vehicle?

- Driving with the code P2603 GMC may lead to engine overheating and potential damage if left unresolved for an extended period. It is recommended to address the issue promptly.

6. Is it safe to continue driving if the Check Engine light is illuminated due to code P2603 GMC?

- It is generally not recommended to drive with the Check Engine light illuminated, as it indicates a potential issue that needs attention. Continuing to drive may result in further damage to the vehicle.

7. How much does it typically cost to repair OBDII code P2603 GMC at a mechanic or dealership?

- The cost of repairing OBDII code P2603 GMC can vary depending on the extent of the issue and labor rates. It is advisable to get quotes from different mechanics or dealerships for an accurate estimate.

8. Can I clear the OBDII code P2603 GMC myself, or do I need a professional to do it?

- You can clear the OBDII code P2603 GMC yourself using an OBDII scanner, which is a simple process. However, if the underlying issue is not addressed, the code may reappear.

9. Will resetting the Check Engine light resolve OBDII code P2603 GMC permanently?

- Resetting the Check Engine light may temporarily clear the code, but if the root cause of the issue is not fixed, the code is likely to reappear. It is important to diagnose and repair the problem to prevent recurrence.

10. How urgent is it to address OBDII code P2603 GMC to prevent further damage to the vehicle?

- It is important to address OBDII code P2603 GMC promptly to prevent potential engine overheating and damage. Ignoring the issue may lead to more costly repairs in the future.