P2803 Transmission Range Sensor “B” Circuit High
OBD-II Trouble Code Technical Description
Transmission Range Sensor "B" Circuit High
What does that mean?
This is a generic powertrain code, which means it covers all makes/models, 1996-newer. However, specific troubleshooting steps will vary depending on the vehicle.
This is a generic powertrain diagnostic trouble code (DTC) in the transmission sub-group. It is a type "B" DTC which means that the powertrain control module (PCM) or Transmission control module (TCM) will not illuminate the check engine light until the conditions to set the code are detected on two consecutive key sequences. ( key on-off, off-on)
The PCM or TCM uses the transmission range sensor, also called the inhibitor switch, to determine the position of the shift lever. If it receives signals that indicate two different gear positions at the same time for more than 30 seconds P2803 will be set. If this occurs twice in a row the check engine light will come on and the transmission will be commanded into "fail-safe" or "limp-home" mode.
Example of an external Transmission Range Sensor (TRS):
TRS image from Dorman
Symptoms & Severity of Code
The check engine light will come on accompanied by an obvious lack of power taking off from complete stops due to the transmission starting in third gear.
Continuing to drive the vehicle could result in severe transmission damage. I recommend getting it repaired immediately to avoid costly internal transmission repairs.
Causes
Potential causes for this code to set are:
Diagnostic and Repair Procedures
The transmission range sensor receives a twelve volt signal from the ignition switch and sends a signal back to the PCM/TCM that is appropriate for the selected position of the gear shifter.
In my experience the most common causes of this code have been a faulty range sensor or misadjusted shift cable/linkage.
Checking this "B" circuit is easiest with a scan tool but if one is not available there are still a few things you can check. Have the key in the on position with engine off. (KOEO) With a digital volt ohm meter you can check each return signal circuit individually by back probing at the sensor with it still connected. Have an assistant shift to each gear one at a time. Each signal circuit should have voltage in one position and one position only. If there is voltage present on any one circuit in more than one gear position suspect a faulty range sensor.
In my experience I have NEVER seen a PCM/TCM be the cause of any range sensor related DTC. This does not mean it is not possible, because it is, it is just not probable. However, I have seen a faulty PCM/TCM that was damaged by a short circuit in a range sensor. If you suspect a fault in the PCM/TCM make sure to look for the cause of the damage before installing a new one to avoid causing the same damage to it.
Related Transmission Range Sensor codes: P2800, P2801, P2802, and P2804.
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"Delete Error Code Permanently, Disable DTC Error Code Function for p2803 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p2803 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p2803.
