What causes the p2251 OBD-II trouble code?
The engine control module (ECM) monitors the negative current control of the O2 sensor heater circuit. If the current cannot be controlled and the voltage does not change on the return wire, then the ECM detects this as an open circuit in the heater circuit for the O2 sensor heater circuit. What causes the P2251 code?
What does a stored code p2251 in PCM mean?
A stored code P2251 means that the powertrain control module (PCM) has detected a negative current discrepancy in the upstream oxygen (O2) sensor for engine bank number one. Bank one is the engine bank that contains the number one cylinder. Sensor 1 denotes the upstream (pre-cat) sensor. The negative current control circuit is a ground circuit.
What to do if p2251 O2 sensor is reset?
Unplug the HO2S in question and use the DVOM to check resistance between the negative current control circuit and any voltage circuits. If there is continuity, suspect a defective HO2S. If the code P2251 continues to be reset, start the engine. Allow it to reach normal operating temperature and idle (with the transmission in neutral or park).
When to use a p2251 malfunction indicator lamp?
If the PCM detects a degree of voltage that is not commiserate with acceptable parameters, a P2251 will be stored and a malfunction indicator lamp (MIL) may be illuminated. Most vehicles will require multiple ignition cycles (with a failure) for MIL illumination.
The engine control module (ECM) monitors the negative current control of the O2 sensor heater circuit. If the current cannot be controlled and the voltage does not change on the return wire, then the ECM detects this as an open circuit in the heater circuit for the O2 sensor heater circuit. What causes the P2251 code?
A stored code P2251 means that the powertrain control module (PCM) has detected a negative current discrepancy in the upstream oxygen (O2) sensor for engine bank number one. Bank one is the engine bank that contains the number one cylinder. Sensor 1 denotes the upstream (pre-cat) sensor. The negative current control circuit is a ground circuit.
Unplug the HO2S in question and use the DVOM to check resistance between the negative current control circuit and any voltage circuits. If there is continuity, suspect a defective HO2S. If the code P2251 continues to be reset, start the engine. Allow it to reach normal operating temperature and idle (with the transmission in neutral or park).
If the PCM detects a degree of voltage that is not commiserate with acceptable parameters, a P2251 will be stored and a malfunction indicator lamp (MIL) may be illuminated. Most vehicles will require multiple ignition cycles (with a failure) for MIL illumination.