P2803 Transmission Range Sensor B Circuit High

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OBD-II DTC Datasheet

Transmission Range B Sensor Circuit High Signal

What does this mean?

This is a generic transmission code which means it covers all makes / models from 1996 onwards. However, specific troubleshooting steps may differ from vehicle to vehicle.

This is a generic transmission diagnostic trouble code (DTC) in a transmission subgroup. This is a Type “B” DTC which means the powertrain control module (PCM) or powertrain control module (TCM) will not illuminate the check engine light until the conditions to set the code are detected on two successive key sequences. (key on-off, off-on)

The PCM or TCM uses a transmission range sensor, also called a lock switch, to determine the position of the gear lever. If it receives signals indicating two different gear positions at the same time for more than 30 seconds, P2803 will be set. If this happens twice in a row, the check engine light will illuminate and the transmission will enter fail-safe or emergency mode.

Example of an external transmission range sensor (TRS): Image of TRS by Dorman

Symptoms and code severity

The check engine light will illuminate when there is an apparent lack of PTO after a complete stop due to the transmission starting in third gear.

Continuing to drive can cause serious damage to the transmission. I recommend getting it repaired immediately to avoid costly repairs to the internal gearbox.

reasons

Possible reasons for setting this code:

Defective transmission range sensor "B".
Incorrect adjustment of the cable / gear lever
Damaged wiring
Incorrect setting of the range sensor "B"
(Rarely) PCM or TCM failure

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 which corresponds to the selected shift position.

In my experience, the most common causes of this code were a faulty range sensor or improper cable / shift lever adjustment.

Checking this "B" circuit is easiest with a scan tool, but if one is not available there are a few more things you can check. Keep the key on with the engine off. (KOEO) With a digital volt ohmmeter, you can test each feedback circuit individually by testing the sensor with the sensor connected. Have an assistant change each gear in turn. Each signal circuit must only be energized in one and one position. If voltage is present on any circuit in multiple gear positions, suspect that the range sensor is faulty.

In my experience, I have NEVER seen the PCM / TCM cause any DTC related to the range sensor. This does not mean that it is not possible, because it is simply unlikely. However, I saw a faulty PCM / TCM that was damaged by a short circuit in the range sensor. If you suspect a malfunction in the PCM / TCM, be sure to find the cause of the damage before installing a new one so as not to cause the same damage.

The associated transmission range sensor codes are P2800, P2801, P2802 and P2804.

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