Technical Description of OBD-II Trouble Code
The circuit controlling Coolant Pump B is open
What does that signify?
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. The CP-B is operated by an electrical signal from the Powertrain Control Module (PCM).
The PCM receives inputs from coolant temperature, intake air temperature, engine RPM, and air conditioning system pressure sensors to determine when and how long it needs to operate the CP-B. Once the PCM has received these inputs, it can modify the signal to the CP-B.
P261A is typically set due to electrical issues with the CP-B circuit. These issues should not be overlooked during troubleshooting, especially when dealing with an intermittent problem.
Troubleshooting steps may vary depending on the manufacturer, type of CP-B, and wire colors.
Related trouble codes for the coolant pump “B” circuit:
Symptoms & Severity
This code usually has a severe impact on the cooling system. Since it is usually an electrical failure, the PCM cannot fully compensate for it. Partial compensation often results in the cooling fans operating at 100% duty cycle all the time.
Symptoms of a P261A code may include:
Causes
Possible causes for this code to be set are:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known problem with a known solution provided by the manufacturer, which can save you time and money during diagnosis.
Next, locate the Coolant Pump B (CP-B) on your particular vehicle. This pump is usually found mounted to the front or top of the engine, inside the wheel wells, or against the bulkhead. Once located, visually inspect the connector and wiring. Look for scraping, rubbing, bare wires, burn spots, or melted plastic. Pull the connector apart and carefully inspect the terminals inside the connector. Check for signs of burning or corrosion. If needed, clean the terminals using electrical contact cleaner and a plastic bristle brush. Let them dry and apply electrical grease where the terminals make contact.
If you have a scan tool, clear the diagnostic trouble codes from memory and see if the P261A code returns. If it does not, then the issue was most likely with the connections.
For this particular code, the most common area of concern is the connections to the relays and the relays themselves, with a pump failure being the second most common cause.
If the code does return, you will need to test the pump and the associated circuits. Typically, there are 2 wires at each coolant pump. First, disconnect the harness going to the coolant pump. Using a Digital Volt Ohm Meter (DVOM), connect one lead of the meter to one terminal of the pump and the other lead to the other pump terminal. The circuit should not be open or shorted. Verify the resistance specifications for your particular vehicle. If the pump motor is either open or shorted (infinite resistance or 0 ohms), replace the coolant pump.
If that test passes, use a DVOM to check if there is 12V in the coolant pump power supply circuit (Red lead to the pump power supply circuit, black lead to a good ground). Use a scan tool that can activate the coolant pump to turn it on. If there is no 12 volts to the pump, repair the wiring from the PCM or relay to the pump, or consider the possibility of a faulty PCM.
If that’s OK, check if there is a good ground at the coolant pump. Connect a test light to 12V battery positive (red terminal) 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 comes on each time the pump is activated. If the test light does not light up, there is a problem with the circuit. If it does light up, wiggle the wiring harness going to the pump to check for an intermittent connection indicated by the test light flickering.
If all previous tests have passed and you continue to get a P261A code, it most likely indicates 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 in order to be installed correctly.
Other similar coolant pump codes include P2600, P2601, P2602, and P2603.
