Table of Contents
Error Code P0059 is defined as Heater Circuit Resistance Bank 2, Sensor 1. This means the PCM (powertrain control module) has detected that the electrical resistance of Bank 2, Sensor 1 of the oxygen sensor is incorrect.
Error Code P0059 is usually set when there is a malfunction in the Bank 2, Sensor 1 oxygen sensor’s (O2) heater circuit, which means the heater is non-operational as it falls outside its predefined parameters. For engines with two cylinder heads, “bank 2” refers to the cylinder bank that doesn’t have the cylinder #1, while “sensor 1” refers to the O2 oxygen sensor found upstream of the catalytic converter.
Though high or low resistance can happen in the control circuit wiring and PCM, there’s a good chance that the problem involves the internal resistance of the actual O2 sensor itself, rather than the PCM’s control circuit. Usually, the resistance will be at 8 Ohms (or close to it), while about 10% variation to either side can trigger this error code and activate the Check Engine light.
There may be no visible or obvious symptoms for error code P0059 in some cases, aside from, of course, the Check Engine light and the stored trouble code. However, for makes and models may experience a more severe case of this error code which results in more obvious symptoms. One of the most visible signs is that, failed O2 sensor of the heater circuit results to longer time to get to operating temperature, which results in increased emissions during cold starts.
Also, the symptoms may depend on the severity of the problem. Some of these symptoms are:
- Drastic increase in fuel consumption
- Engine power loss
- Over-fueling through extended periods results in oil dilution
- Black smoke coming out from the tail pipe
- Hard starting
- Rough idling
- Carbon deposit buildup reducing spark plug life
The PCM continues to monitor the heater circuit for all O2 sensors of the vehicle. If it detects incorrect resistance in the Bank 2 Sensor 1 O2 sensor, then it will trigger the error code. And the most common cause of that is a problem with the wiring for the O2 sensor circuit. Other possible causes include:
- Connectors and wirings damaged by heat or impact with road debris
- Defective O2 sensors
- Blown O2 sensor fuse
- Open or short circuit in O2 sensor harness, internal O2 sensor or PCM
- Failing PCM (rare)
How to Check
To diagnose for this error code, mechanics conduct a thorough visual inspection of the sensor harness and look for signs of damage. The damage can be the trigger of the error code.
If there are no damages found, mechanics measure the O2 sensor’s heater circuit. This is where they will need the service manual of the vehicle to get the exact specifications for the resistance of the engine. If the test shows sensor is out of the set specifications, then that’s the cause of the problem.
If the sensor is in good condition, mechanics connect a test lamp to the O2 sensor heater circuit (rather than to the O2 sensor harness). If the test light shines bright, then that confirms that the problem is in the heater circuit.
If the sensor test shows normal results, and the vehicle side test shows to be okay based on the test light, then they would look to the connection between the O2 sensor harness and vehicle side of the harness.
Damage or corrosion on the terminals that causes poor connection can also trigger this error code.
How to Fix
The most common fix for this error code is replacing the faulty O2 sensor.
The next steps for repairs are fixing the problems on the wiring. As said earlier, chaffed wiring, misrouted harness, etc., can trigger the error code.
The most common mistake in repairing Error Code P0059 is assuming that replacing the Bank 2, Sensor 1 O2 sensor without conducting diagnostic tests can fix the problem.
This error code may be less severe than the others, as there are no obvious drivability issues, but it can cause your vehicle to fail an emission test.