What does it mean?
This diagnostic code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by make/model.
This is a generic powertrain diagnostic code (DTC) in the transmission subgroup. It is a “B” type DTC, meaning the Powertrain Control Module (PCM) or Transmission Control Module (TCM) will not illuminate the Check Engine light until the code setting conditions are detected on two consecutive key cycles (on-off, off-on).
The PCM or TCM uses the transmission range sensor, also called the inhibitor switch, to determine the gear lever position. If it receives signals indicating two different gear positions at the same time for more than 30 seconds, P0708 will be set. If this happens twice in a row, the Check Engine light will illuminate, and the transmission will be commanded into a “fail-safe” or “limp-home” mode.
Symptoms
and code severity
The Check Engine light will illuminate, accompanied by a noticeable lack of power when pulling away from complete stops because the transmission starts in third gear.
Continuing to drive the vehicle can lead to serious transmission damage. I recommend having it repaired immediately to avoid costly internal transmission repairs.
Causes
Causes
possible for setting this code are as follows:
Faulty transmission range sensor
Poorly adjusted gearshift cable/linkage
Damaged wiring
Poorly adjusted range sensor
(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 appropriate for the selected gear lever position.
In my experience, the most common causes of this code have been a faulty range sensor or a poorly adjusted gearshift cable/linkage.
Checking this circuit is easier with a scan tool, but if one is not available, there are still a few things you can check. Keep the key in the ON position with the engine off (KOEO). With a digital voltmeter, you can check each individual return signal circuit by backprobing the sensor while it is still connected. Have an assistant shift into each gear one by one. Each signal circuit should have voltage in one and only one position. If there is voltage on a 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 a DTC related to a range sensor. This doesn’t mean it’s not possible, because it is, it’s just not likely. However, I have seen a faulty PCM/TCM that was damaged by a short circuit in a range sensor. If you suspect a PCM/TCM failure, be 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: P0705, P0706, P0708, P0708 and P0709