Technical Description of OBD-II Trouble Code
Intermittent Fuel Pump Secondary Circuit
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The fuel pump is powered by the fuel pump relay. When the powertrain control module (PCM) activates the fuel pump relay, it supplies voltage to the fuel pump, pressurizing the fuel system. Some vehicles have a feedback circuit on the fuel pump supply circuit, which is a circuit spliced into the voltage feed to the fuel pump. This splice is usually located near the PCM.
The PCM monitors this feedback circuit to ensure that the fuel pump receives the proper voltage. When it activates the fuel pump relay, it expects to see battery voltage on the feedback circuit. If the PCM detects an unexpected intermittent problem with the signal when the fuel pump is not activated, it may set the P0233 code.
Symptoms
The symptoms of a P0233 DTC may include:
Causes
The potential causes of a P0233 code include:
Possible Solutions
With a P0233 code, it is possible for the fuel pump to run continuously even with the ignition off. If you can hear the fuel pump running in this case, you may be able to disregard some of the following checks. Turn the key on with the engine off (KOEO) and wait for a few seconds. This allows the PCM to complete its fuel pump pre-cycle. Now, if you have a scan tool, observe the FP VOLTAGE FEEDBACK reading in the data stream. This reading indicates the voltage that the fuel pump is receiving.
If you do not have access to a scan tool, use a voltmeter to measure the FP voltage at the fuel tank. If your reading shows any voltage present at the fuel pump with KOEO (or if you can hear the pump running), remove the FP relay. If the voltage remains or the fuel pump continues to run, there may be a short to voltage on the FP voltage supply circuit or feedback circuit. Repair as necessary. If the voltage disappears (or the pump stops running) with the FP relay removed, try replacing the relay with a spare one. If the voltage disappears after reinstalling the spare relay, the relay was faulty due to a short. However, if the voltage is still present, suspect that the PCM FP relay control circuit is shorted to ground.
To check for a short to ground on the PCM FP relay control (ground driver) circuit, remove the FP relay and measure the continuity between a good ground and the PCM FP relay control. There should be no continuity to ground with KOEO (after the FP pre-cycle is completed). If there is continuity to ground, the wire is shorted. Find the short to ground and repair as necessary. If you cannot find a physical short, it may be necessary to cut the FP relay control wire close to the PCM connector where it is easy to repair, and check for continuity to ground with KOEO coming out of the PCM. If there is no continuity, the wire is shorted in the harness. However, if continuity exists, the driver may be internally shorted to ground and the PCM may need to be replaced.
