Fault code P07B8 is called “Transmission Park Position Sensor/Switch “B” Circuit Open” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.
Technical description and explained code P07B8
Diagnostic Trouble Code P07B8 (DTC) refers to the transmission parking switch. This is one of several possible codes associated with the transmission parking position “B” sensor circuit.
The error indicates that the transmission control module (PCM) has detected a fault that affects the operation of the transmission parking position sensor circuit. In this particular case, the problem is an open circuit.
The transmission parking position sensor circuit is designed to monitor the status of the transmission. This circuit sends a signal to the PCM when the transmission is shifted into park position.
Depending on the specific vehicle, this error is usually a safety feature. Preventing the starter from engaging the automatic transmission when the transmission is in gear.
Code P07B8 is set by the PCM when an open circuit is detected in the “B” parking position sensor circuit. When the code is set, the malfunction indicator lamp on the instrument panel lights up.
Symptoms of vehicle malfunctions
The main signal that an error P07B8 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.
It can also be warning signs such as:
- Check engine control lamp on the control panel will light up (the code will be recorded in the memory as a malfunction).
- The car cannot be started, the starter does not start.
- The starter will only engage when a gear is engaged.
- Unable to shift gears from park.
- Transmission cannot shift into park.
The severity of error P07B8 varies from medium to serious, depending on the specific fault. The engine may stop starting. It is also possible for the transmission to go into emergency operation mode. If the error is not corrected, the severity level may increase.
Factors that can cause this error code
The error code P07B8 can mean that one or more of the following problems have occurred:
- Transmission parking position sensor is defective.
- Short circuit, open circuit, damaged or faulty wiring.
- Damaged sensor connector.
- Sometimes faulty PCM module is the cause.
How to fix or reset OBD-2 code P07B8
Some suggested steps for troubleshooting and fix the error code P07B8:
- Read all data and error codes stored in the PCM memory with an OBD-II scan tool.
- Reset the stored codes and test drive the vehicle.
- If the error is back, check the connectors as well as the wiring for damage or poor contact.
- Check the transmission parking position sensor, replace if necessary.
- If the code is still active, a faulty PCM may be suspected.
Diagnose and repair of problems
Always check the technical service bulletins (TSB) for your particular vehicle first. The P07B8 problem may already be a known problem with a known fix issued by the manufacturer. This can save you time and money during diagnosis.
The next step is to locate the transmission parking position sensor. Once found, visually inspect the connector and wiring. Look for scratches, scuffs, exposed wires, burn stains, or melted plastic.
Disconnect the connector and carefully inspect the terminals inside the connector. Look to see if they look burnt or have a green tint indicating corrosion. If you need to clean the terminals, use an electrical contact cleaner and a plastic-bristle brush. Allow to dry and apply electrical grease to the contact areas of the terminals.
Using a diagnostic tool, clear the trouble codes from the memory and see if error P07B8 returns. If the code returns, we will need to test the sensor and associated circuits.
Wiring test
With the ignition key off, disconnect the electrical connector on the sensor. Connect a digital voltmeter. The black wire to ground and the red wire to the signal terminal on the transmission parking position sensor wiring harness connector.
Turn on the ignition key. Depending on the manufacturer’s specifications, the voltmeter should show either 12 volts or 5 volts. Jerk the connection and see if the reading changes. If the voltage is incorrect, replace the faulty wires or connector.
Check the sensor
Connect one ohmmeter lead to the signal terminal on the transmission parking position sensor and the other to ground. Check the resistance against the manufacturer’s specifications. Jiggle the connector on the sensor, checking the resistance. If the ohmmeter reading differs from the manufacturer’s recommendation, replace the sensor.
If the wiring and sensor tests are done, but you are still getting code P07B8. You need to look at the PCM / TCM module as well as internal transmission failures. But you need to do this after replacing the sensor. More often than not, it is the one that is the problem.
If you are unsure, ask a qualified automotive diagnostician for help.
On which vehicles does this problem occur most frequently
Fault code P07B8 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:
- Chevrolet
- Dodge
- Ford
- Land Rover
- Toyota
- Volkswagen
Fault code P07B8 can sometimes be found with other errors. The most common are the following: P07B9, P07BA, P07BB, P07BC, P07BD, P07BE.
