P2602 — Coolant Pump “A” Control Circuit Low #

Note: The code label may vary depending on the vehicle manufacturer.

• Coolant Pump “A” Control Circuit Low (Generic/GM)
• Auxiliary Coolant Pump Control Circuit Low (Ford)
• Electric Coolant Pump “A” Control Circuit Low (Mercedes-Benz)

Summary of DTC P2602 #

DTC P2602 is a diagnostic trouble code indicating that the engine control module (ECM) or powertrain control module (PCM) has detected a low voltage or current condition in the Coolant Pump “A” control circuit. This electric pump, sometimes called an auxiliary water pump, helps circulate coolant, especially in turbocharged or hybrid vehicles for better engine and component cooling. A “low” circuit condition means the ECM is seeing less electrical activity than expected—often suggesting an open circuit, high resistance, or a failed component. This code can trigger the check engine light and, if ignored, may affect the vehicle’s ability to manage engine temperature efficiently. The specific roles and naming of this circuit vary by manufacturer, but the root issue remains the same—insufficient electrical activity on the coolant pump “A” control circuit.

Common Symptoms for Code P2602 #

When P2602 is stored, symptoms can range from subtle to obvious, depending on your vehicle and driving conditions. Some drivers may only notice the check engine light, while others could experience more pronounced effects, especially during hot weather or demanding driving scenarios.

• Illuminated check engine light (MIL)
• Engine runs hotter than usual or overheats under load
• Reduced heater performance (especially at idle or low speeds)
• Possible limp mode activation (especially on hybrids or vehicles with sensitive thermal management)
• Electric coolant pump not running when commanded
• Unusual fan operation (running more often or for longer)

Probable Causes for P2602 (Most to Least Common) #

The most frequent causes of P2602 relate to electrical faults or pump failure. Understanding the likely culprits can save you hours under the hood.

1. Faulty electric coolant pump “A” (burned out or seized motor)
2. Open or high-resistance wiring/connectors in the coolant pump control circuit
3. Blown fuse or relay related to the coolant pump
4. Corroded or loose ground connections
5. PCM/ECM failure or internal circuit issue (rare)
6. Coolant contamination causing electrical shorts at the pump connector

Step-by-Step Diagnostic for P2602 #

A systematic approach is essential for accurate diagnosis. Rushing can lead to missed details or unnecessary part replacements. Here’s a proven workflow:

1. Scan for additional codes: Address any related codes (especially cooling system or sensor codes) first.
2. Visual inspection: Check the coolant pump “A” and its wiring for visible damage, corrosion, or coolant leaks.
3. Check the fuses and relays: Locate the fuse/relay for the auxiliary coolant pump and test for continuity and proper operation.
4. Test pump electrical supply: With the ignition on, use a multimeter to verify voltage and ground at the pump connector when the system is commanded on.
5. Check circuit resistance: Measure resistance in the wiring harness between the PCM and the pump; look for open, short, or high resistance.
6. Command the pump with a scan tool: If available, use OEM-level diagnostic software to activate the pump and observe its response and current draw.
7. Bench test the pump (if removed): Power the pump directly from a 12V source to confirm operation.
8. PCM/ECM testing: If all else tests good, suspect a rare fault in the PCM/ECM or its control circuits.

Possible Repairs for P2602 #

Once diagnosed, the repair path is usually straightforward. Each fix aligns with the root cause found during your troubleshooting.

• Replace the faulty electric coolant pump “A”
• Repair or replace damaged wiring/connectors in the pump circuit
• Replace blown fuse or faulty relay
• Clean or tighten ground connections related to the pump
• Repair coolant leaks affecting the pump’s electrical connector
• In rare cases, replace or reprogram the PCM/ECM

Is It Safe to Drive with Code P2602? #

Limited. Proceed with caution. While some vehicles will not immediately overheat, a non-functioning electric coolant pump “A” can cause engine overheating—especially in stop-and-go traffic, hot weather, or if your vehicle is turbocharged or hybrid. In the short term, you may be able to reach a service location, but ongoing driving risks severe engine or component damage. If the engine temperature gauge climbs or warning lights appear, stop immediately and seek assistance.

Vehicles Most Commonly Affected by P2602 #

Some platforms use auxiliary or electric coolant pumps more extensively, making them more prone to this code—especially as these pumps age.

• BMW (especially turbocharged and hybrid models, e.g., 3 Series, 5 Series, X Series)
• Mercedes-Benz (C-Class, E-Class, S-Class with electric water pumps)
• Volkswagen and Audi (turbo models with secondary pump)
• Ford (hybrid systems, Escape, Fusion)
• GM (Chevrolet Volt, Malibu Hybrid, and models with electric auxiliary pumps)
• Toyota/Lexus hybrids

Common Mistakes & Best Practices for P2602 #

Avoiding the typical pitfalls and following proven best practices can save time and money. Here’s what technicians and DIYers frequently get wrong—and how to do better.

• Replacing the pump without checking for blown fuses, relays, or wiring faults
• Overlooking corroded connectors or grounds (especially in humid environments)
• Ignoring coolant leaks at or near the pump, which can cause electrical issues
• Neglecting to clear the code and test system operation after repair
• Failing to use a scan tool’s active test function to confirm pump operation
• Assuming the PCM/ECM is the problem before thoroughly checking the basics

Express FAQ for P2602 #

Q: Will P2602 cause my vehicle to overheat right away?
A: Not always, but the risk increases dramatically in hot weather, traffic, or under heavy load. Monitor engine temperature closely and avoid strenuous driving until repaired.

Q: Can I bypass or jump the electric coolant pump?
A: Bypassing is not recommended. Doing so may damage the pump, wiring, or control module. Always diagnose and repair the root cause.

Q: Does P2602 affect my emissions test?
A: If the check engine light is on, your vehicle will fail most emissions inspections—even if the code is not directly emissions-related.

Q: Is this a common failure as my vehicle ages?
A: Yes, electric coolant pumps and their wiring are wear items—especially in vehicles over 7–10 years old or with frequent short trips.