Symptoms
and Severity
The severity is generally high due to its impact on the cooling system. Since it is typically an electrical failure, the PCM cannot fully compensate for it. Partial compensation usually means the cooling fans run continuously (100% duty cycle).
Symptoms of a P2602 code may include:
- Malfunction indicator light illuminated
- Overheating
- Air conditioning system not functioning properly
Causes
Potential causes for this code are as follows:
- Open circuit in the coolant pump – likely
- Failed coolant pump – likely
- Failed PCM – unlikely
Diagnostic and Repair Procedures
A good starting point is always to check the Technical Service Bulletins (TSBs) for your specific vehicle. Your issue might be a known problem with a published fix from the manufacturer, which can save time and money during diagnosis.
Next, locate the B coolant pump (CP-A) on your specific vehicle. This pump is typically mounted at the front of the engine, on top of the engine, inside the wheel wells, or against the firewall. Once located, visually inspect the connector and wiring. Look for scratches, rubbing, exposed wires, burns, or melted plastic. Disconnect the connector and carefully inspect the terminals (the metal parts) inside. Check if they appear burnt or have a greenish tint indicating corrosion. Use electrical contact cleaner and a plastic-bristled brush if terminal cleaning is necessary. Allow it to dry and apply electrical grease where the terminals make contact.
If you have a scan tool, clear the diagnostic codes from memory and see if the P2602 code returns. If it does not, the connections were likely the issue.
For this particular code, the most common area of concern is the relays and relay connections, with pump failure being the second most common.
If the code returns, we will need to test the pump and related circuits. Typically, there are 2 wires for each coolant pump. First, disconnect the harness going to the coolant pump. With a digital volt-ohm meter (DVOM), connect one meter lead to one terminal of the pump. Connect the remaining meter lead to the other pump terminal. It should not be open or shorted. Check the resistance specifications for your specific vehicle. If the pump motor is open or shorted (infinite resistance or no resistance/0 ohms), replace the coolant pump.
If this test passes, use a DVOM to check for 12V at the coolant pump power circuit (red lead to the pump power circuit, black lead to a good ground). With a scan tool capable of activating the coolant pump, turn on the coolant pump. If there is no 12 volts at the pump, repair the wiring from the PCM or relay to the pump, or possibly a faulty PCM.
If that is okay, check the coolant pump ground circuit. Connect a test light to the positive 12V battery terminal (red terminal) and touch the other end of the test light to the ground circuit going to the coolant pump circuit ground. Using the scan tool to activate the coolant pump, check if the test light illuminates each time the scan tool activates the pump. If the test light does not illuminate, it would indicate a circuit problem. If it does light up, wiggle the wiring harness going to the pump to see if the test light flickers, indicating an intermittent connection.
If all previous tests pass and you continue to get a P2602, it would most likely indicate a faulty coolant pump, although a faulty PCM cannot be ruled out until the coolant pump has been replaced. If in doubt, seek assistance from a qualified automotive diagnostician. PCMs need to be programmed or calibrated to the vehicle to be installed correctly.
Other similar coolant pump codes include P261A, P261B, P261C, and P261D.