Code Severity and Symptoms
The severity is generally severe due to its impact on the cooling system. Since it’s typically an electrical failure, the PCM cannot fully compensate for it. Partial compensation usually means the engine has a fixed idle speed (generally around 1000 – 1200 RPM).
Symptoms of a P2102 engine code may include:
- Malfunction indicator light illuminated
- Fixed idle speed
- Unable to accelerate the engine
Causes
Typically, the causes for this code to set are as follows:
- Open or short circuit in the throttle actuator circuit – likely
- Failed throttle actuator – 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 known fix published by the manufacturer and could save you time and money during diagnosis.
Next, locate the Throttle Actuator A (TA-A) on your specific vehicle. This actuator is typically found mounted on 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 chafing, rubbing, bare wires, burns, or melted plastic. Disconnect the connector and carefully inspect the terminals (the metal parts) inside the connector. See if they appear burnt or have a greenish tint indicating corrosion. Use electrical contact cleaner and a plastic bristle brush if cleaning the terminals is necessary. Let it dry and apply electrical grease where the terminals make contact.
If you have a scan tool, clear the diagnostic codes from the memory and see if the P2102 code returns. If it does not, the connections were likely your problem.
For this code, this is the most common area of concern, just like relay/connections to relays, with actuator failure being a close second.
If the code returns, we will need to test the actuator and related circuits. Typically, each throttle actuator has 2 wires. First, disconnect the wiring harness going to the throttle actuator. With a digital volt-ohm meter (DVOM), connect one meter lead to one terminal of the actuator. Connect the remaining meter lead to the other terminal of the actuator. It should not be open or shorted. Check the resistance specifications for your specific vehicle. If the actuator motor is open or shorted (infinite resistance or no resistance/0 ohms), replace the throttle actuator.
If this test passes, with a DVOM, verify that you have 12V at the throttle actuator power circuit (red lead to the actuator power circuit, black lead to a good ground). With a scan tool that can activate the throttle actuator, turn on the throttle actuator. If there is no 12 volts at the actuator, repair the wiring from the PCM or relay to the actuator, or possibly a faulty PCM.
If that checks out, ensure you have a good ground at the throttle actuator. Connect a test light to the positive 12V battery (red terminal) and touch the other end of the test light to the ground circuit going to the throttle actuator circuit ground. Using the scan tool to actuate the throttle actuator, check if the test light illuminates each time the scan tool actuates the actuator. If the test light does not illuminate, it would indicate a circuit problem. If it does illuminate, wiggle the wiring harness going to the actuator to see if the test light flickers, indicating an intermittent connection.
If all previous tests have passed and you continue to get a P2102, it would most likely indicate a failing throttle actuator, although a faulty PCM cannot be ruled out until the throttle actuator 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.