What Does Code P0055 Mean When this code is set it means that the Engine Control Module (ECM) has detected a problem with the amount of resistance in the heater circuit for the third oxygen sensor on bank one of the engine. engine code P0055P0055 fixobd P0055dtc P0055obd code P0055obd2 P0055P0055 car codediagnostic code P0055car code P0055check engine code P0055fehlercode P0055P0055 fiatcodigo P0055codigo falla P0055P0055 kody błędówcodigo de falla P0055Possible symptoms Engine Light ON (or Service Engine Soon Warning Light) Possible causes Faulty Heated Oxygen Sensor Bank 1 Sensor 3 Heated Oxygen Sensor Bank 1 Sensor 3 harness is open or shorted Heated Oxygen Sensor Bank 1 Sensor 3 circuit poor electrical connection Troubleshooting P0055 NOTE #1: Bear in mind that the oxygen sensor itself forms part of the control circuit, which is why it must be tested along with the wiring when resistance tests are carried out. NOTE #2: Diagnosing code P0055 requires that the engine be in perfect running order, with no misfiring, rich-, or lean running conditions, or vacuum and exhaust leaks present that could influence the proper working of any oxygen sensor. If there are other codes present along with P0055, these codes must be resolved before starting a diagnostic procedure for code P0055. Step 1 Record all stored fault codes, along with all available freeze frame data. This information could be very helpful if an intermittent fault is diagnosed later on. Step 2 Perform a thorough visual inspection of all wiring associated with the affected sensor. Consult the manual to determine the function, color-coding, location, and routing of all wires in the circuit, and look for shorted, burnt, damaged, or broken wiring and connectors. Pay particular attention to the routing of the wiring, since unsecured and misrouted wiring can easily burn against hot exhaust components. Repair wiring and/or connectors as required, but be sure to route all wiring as far away from the exhaust system as possible. Step 3 If no visible damage to the wiring is found, perform continuity, resistance, ground, and reference voltage checks on all associated wiring. Consult the manual on the exact values required for the application being worked on, but be sure to disconnect the sensor from the PCM before starting continuity checks to prevent damage to the controller. Since code P0055 indicates a resistance issue, pay particular attention to the resistance values. If the circuit is fused, check the resistance in both the reference voltage and signal voltage wires; replace the wiring if obtained values do not fall within the manufacturer’s specifications. If the circuit is not fused, the PCM is supplying the reference voltage (and sometimes the ground as well) so consult the manual on the relevant pin number and location in the PCM connector. Check for continuity and resistance from this pin to the corresponding pin in the connector on the end of the wiring harness. Compare obtained readings with those stated in the manual, and replace the affected wiring if obtained values differ from those stated in the manual. At this point it also a good idea to confirm that the oxygen sensor reference voltage is the same as the battery voltage, i.e., 12.6V to 13.8V to eliminate battery and charging system issues as the cause of long warm-up times of oxygen sensor heater elements. Low input voltages may not always cause code P0055, but it is easy to misinterpret long warm-up times as resistance issues. NOTE: Avoid repairing wiring, since poorly executed repairs could cause high resistance and continuity issues later on. The better option is always to replace wiring, as opposed to repairing it. Step 4 If all electrical values fall within manufacturer’s specifications, or after repairs had been made, clear all codes and test the system again to see if the code returns. If it does return, it is almost certain that the sensor itself is defective. Remove the affected sensor from the exhaust system, and test its resistance. Note that the manual will state the exact resistance value, and the obtained reading must match this value exactly. Close enough is not good enough; oxygen sensors require a specific resistance to work properly, so replace the sensor if there is any doubt about its internal resistance. NOTE: Resist the temptation to replace the sensor with a cheap aftermarket part. These parts almost never conform to OEM specifications, meaning that not using OEM replacement sensors could cause a speedy recurrence of the problem. Step 5 If the sensor is replaced, clear all codes still present, and test drive the vehicle with a suitable scanner connected to monitor the operation of the sensor in real time. Note that during normal operation, the signal voltage will never be static; after the PCM enters closed loop operation, it will change continually from around 100 millivolts to about 900 millivolts, depending on the engine load and speed. However, assuming that no misfiring, vacuum, or exhaust issues are present, this fluctuation is dependent on both the resistance of the control circuit and the sensor itself, meaning that a persisting, or intermittent resistance issue could affect the signal voltage. Both high and low resistances could cause the heater element not to work properly, which will ultimately affect the signal voltages generated. Step 6 Note that intermittent problems can sometimes be extremely difficult to find and repair. In some cases, it may be necessary to allow the fault to worsen before an accurate diagnosis and definitive repair can be made. Searches related to P0055 p0055 nissan nissan 0055 system normal c342d code p0055 ho2s heater resistance c0055 bank 1 sensor 3 location p0056 p0059
