Technical Description of OBD-II Trouble Code
The control circuit for Coolant Pump “B” is experiencing high voltage.
What does that mean?
This generic powertrain/engine diagnostic trouble code typically applies to all OBDII equipped engines with electric coolant pumps, but is more commonly found in certain hybrid vehicles manufactured by Ford, Honda, Nissan, and Toyota.
The Coolant Pump B (CP-B) is usually located at the front or top of the engine, inside the wheel wells, or against the bulkhead. It is operated by an electrical signal from the Powertrain Control Module (PCM).
The PCM receives voltage signals from various sensors, including coolant temperature, intake air temperature, engine RPM, and air conditioning system pressure sensors. Based on these inputs, the PCM determines when and how long to operate the CP-B by modifying the signal sent to it.
The P261D trouble code is typically set due to electrical issues in the CP-B circuit. These issues should not be overlooked during troubleshooting, especially when dealing with intermittent problems.
The troubleshooting steps may vary depending on the manufacturer, type of CP-B, and wire colors.
Other related trouble codes for the coolant pump “B” circuit include:
Symptoms & Severity
This trouble code usually has a severe impact on the cooling system. Since it is typically an electrical failure, the PCM cannot fully compensate for it. As a result, the cooling fans may operate continuously at 100% duty cycle.
Symptoms of a P261D code may include:
Causes
Possible causes for this code to be set are:
Diagnostic and Repair Procedures
A good starting point is to check for technical service bulletins (TSB) specific to your vehicle. There may be a known issue with a known fix provided by the manufacturer, which can save time and money during diagnosis.
Next, locate the Coolant Pump B (CP-B) on your vehicle and visually inspect the connector and wiring. Look for any signs of scraping, rubbing, bare wires, burn spots, or melted plastic. Disconnect the connector and carefully inspect the terminals inside for any signs of burning or corrosion. Clean the terminals if necessary using electrical contact cleaner and a plastic bristle brush. Apply electrical grease to the terminals before reconnecting.
If you have a scan tool, clear the diagnostic trouble codes from memory and check if the P261D code returns. If it does not, the issue was likely related to the connections.
For this particular code, the most common area of concern is the connections and relays, with a pump failure being the second most likely cause.
If the code does return, further testing of the pump and associated circuits is necessary. Typically, there are 2 wires connected to each coolant pump. Using a Digital Volt Ohm Meter (DVOM), check the resistance between the terminals of the pump. It should not be open or shorted. Refer to the resistance specifications for your specific vehicle. If the pump motor is open or shorted, replace the coolant pump.
If the pump test passes, use a DVOM to check if there is 12V to the coolant pump power supply circuit. If there is no 12 volts, repair the wiring from the PCM or relay to the pump, or consider a possible PCM failure.
Next, check for a good ground at the coolant pump. Connect a test light to the positive terminal of a 12V battery and touch the other end of the test light to the ground circuit going to the coolant pump. Use the scan tool to activate the coolant pump and see if the test light illuminates each time the pump is activated. If the test light does not illuminate, there is a problem with the circuit. If it does illuminate, wiggle the wiring harness going to the pump to check for intermittent connections.
If all previous tests have passed and the P261D code persists, it is likely a failed coolant pump. However, a failed PCM cannot be ruled out until the coolant pump has been replaced. If unsure, seek assistance from a trained automotive diagnostician. PCMs must be programmed or calibrated to the vehicle for proper installation.
Other similar coolant pump codes include P2600, P2601, P2602, and P2603.
