P2602 Code Symptoms, Causes, Diagnosis and Repair Costs Guide

P2602 Code: Symptoms, Causes, and How to Resolve It

Your vehicle’s temperature gauge climbs toward the red zone, a warning light flashes, and a message appears that the coolant pump is malfunctioning. Those are the first clues that the engine control module (ECM) has logged a P2602 – Coolant Pump A Control Circuit Low fault. The ECM monitors the voltage supplied to the electric coolant pump; when that voltage drops below the programmed threshold, the code is set. Because the pump’s primary job is to circulate coolant through the engine and radiator, a low‑voltage condition can quickly lead to inadequate cooling, overheating, and potential engine damage if left unchecked. Prompt identification of the underlying cause—whether wiring, a fuse, the pump motor itself, or the pump‑control module—prevents costly repairs and keeps the cooling system operating as engineered.

Symptoms

• Overheating warning light or “engine temperature high” message on the dash.
• Coolant pump fault indicator (often a separate icon or text).
• Engine coolant temperature gauge climbing above normal operating range (typically >220 °F/104 °C).
• Loss of coolant circulation noticed after the vehicle idles or during short trips; the engine may run hotter after a few minutes.
• In some models, a reduced fan speed or intermittent fan operation because the ECM may command the fan to compensate for low pump flow.

These signs appear when the pump cannot maintain proper flow, forcing the ECM to alert the driver and log P2602.

Why Coolant Pump A Control Circuit Low Occurs

Damaged Wiring or Connector Issues

Corrosion, chafing, or broken strands in the pump’s power wire can create a high‑resistance path, dropping voltage below the ECM’s minimum threshold. A loose connector pin or water intrusion in the harness can produce intermittent low‑voltage readings, triggering the code sporadically.

Blown Fuse or Faulty Relay

The coolant pump circuit is protected by a dedicated fuse (often 10 A–20 A) and a relay that switches power on and off. A partially blown fuse or a relay that fails to close fully will limit voltage to the pump, causing the ECM to detect a low‑voltage condition.

Failed Coolant Pump Motor

Electric coolant pumps contain an internal motor and a control PCB. When the motor windings develop a short or open circuit, the pump draws less current, and the voltage at the ECM’s sense point drops. The pump may still spin slowly or not at all, reducing coolant flow.

Pump‑Control Module Malfunction

Modern engines use a dedicated pump‑control module that receives commands from the ECM and drives the pump motor. Internal component failure—such as a damaged MOSFET or damaged voltage regulator—can prevent the module from delivering the required voltage, even if the wiring and fuse are intact.

Grounding Problems

A poor ground strap or corroded chassis ground can raise the reference voltage for the pump circuit. The ECM compares pump voltage to ground; an elevated ground potential mimics a low‑voltage condition and sets P2602.

Diagnostic and Repair Procedures

1. Retrieve the code with a professional scan tool. Confirm P2602 and check for related codes (e.g., P2603 – Coolant Pump B Control Circuit Low) that may indicate a broader cooling‑system issue.
2. Inspect the coolant pump fuse and relay.

– Measure fuse resistance; replace if open or borderline.

– Swap the relay with an identical unit from another circuit to verify operation.

1. Perform a visual wiring check.

– Follow the pump power wire from the ECM to the pump, looking for cracks, abrasions, or water intrusion.

– Disconnect the connector, inspect pins for corrosion, and reseat firmly.

1. Voltage test at the pump connector.

– With the ignition ON and the pump commanded ON (often by cycling the HVAC or AC), measure voltage between the power and ground pins.

– Expected voltage is typically 12 V ± 0.5 V; anything below 11 V indicates a low‑voltage condition.

1. Ground continuity test.

– Use a multimeter to verify that the pump ground pin shows less than 0.1 Ω to chassis ground.

1. Pump motor resistance check.

– Disconnect the pump and measure resistance across the motor terminals; values outside the manufacturer’s specification (often 2–5 Ω) suggest motor failure.

1. Pump‑control module communication test.

– Access the module via the scan tool and request live data. Look for “Pump Voltage” or “Pump Current” parameters.

– If the module reports abnormal values or fails to respond, the module may need reprogramming or replacement.

1. Repair or replace the faulty component.

– Wiring/connector repair: splice or replace damaged sections, apply dielectric grease, and secure with zip ties.

– Fuse/relay replacement: install the correct amperage fuse and a new relay if the original is defective.

– Pump motor replacement: remove the pump assembly, install a new motor, and verify proper operation.

– Pump‑control module replacement: source a VIN‑matched module, have it programmed to the vehicle’s calibration, and install.

1. Clear codes and test drive.

– Erase the P2602 code, then monitor coolant temperature and pump operation for at least 30 minutes of varied driving conditions.

Typical costs

• Wiring repair: $50‑$150 for parts and labor.
• Fuse/relay: $10‑$30 for parts, $30‑$60 labor.
• Coolant pump motor: $250‑$400 plus $150‑$250 labor.
• Pump‑control module replacement: $600‑$900 for the module, $200‑$300 labor; programming may add $100‑$150 if not pre‑programmed.

When Replacement Makes Sense

If voltage tests reveal that the pump‑control module consistently supplies insufficient power despite sound wiring, a solid ground, and a healthy pump motor, the module itself is the likely point of failure. Internal component degradation—such as a burnt MOSFET or failed voltage regulator—often cannot be repaired reliably. In these cases, replacing the module restores proper voltage control and eliminates intermittent low‑voltage faults that can lead to overheating.

Modern control modules are complex and integrated with security and immobilizer systems. That’s why choosing a replacement isn’t only about the hardware—it’s about correct programming and compatibility. Flagship One specializes in VIN‑matched control modules, providing a plug‑and‑drive solution backed by warranty. Their units are pre‑programmed to match your vehicle’s software version, ensuring seamless integration and eliminating the need for dealer‑only re‑coding.

Preventive Maintenance

• Inspect coolant pump wiring annually during routine under‑hood checks. Look for signs of wear, chafing, or moisture accumulation, especially near the radiator and engine bay heat shields.
• Verify fuse and relay health at each service interval. Replace any fuse that shows discoloration or a filament break.
• Maintain proper coolant level and quality. Low coolant can cause the pump to run dry, increasing electrical load and heat on the pump motor.
• Clean the pump inlet and radiator fins to ensure unrestricted flow. Debris buildup forces the pump to work harder, potentially stressing the motor and its control circuit.
• Use a quality scan tool during regular diagnostics to catch emerging low‑voltage trends before they trigger a full‑scale overheating event.