P081B: Starter Disable Circuit High

What Does The P081B Code Mean?

If your vehicle has stored a code P081B, it means that the powertrain control module (PCM) has detected a degree of voltage that is lower than expected in the starter disable switch circuit. This type of code may be applicable to vehicles with manual or automatic transmissions.

The starter disable switch is usually a single circuit, open/closed switch which interrupts voltage between the ignition switch and the starter solenoid if the clutch is not depressed, the transmission (manual) is not in neutral, or the transmission (automatic) is not in park. Vehicle applications with an automatic transmission may have the starter disable switch integrated into the neutral safety switch or shift selector switch. The transmission control module (TCM) or the PCM monitor starter disable circuit voltage with the ignition in the ON position. The TCM may be a stand alone module or part of the PCM.

If the PCM detects that starter disable switch circuit voltage is not within allowable parameters, a code P081B may be stored and a malfunction indicator lamp (MIL) illuminated. Multiple ignition cycles (with a failure) may be required for MIL illumination.

What Are The Symptoms Of The P081B Code?

Symptoms of a P081B trouble code may include:

• Engine will not start
• Engine starts with the transmission in gear
• No symptoms may be exhibited

What Are The Potential Causes Of The P081B Code?

Causes for this code may include:

• Defective starter disable switch
• Shorted or open wiring or connectors in starter disable switch circuit
• Faulty PCM or a programming error

How Serious Is This P081B Code?

A stored code P081B could be accompanied by a no-start condition and also indicates that either an electrical issue or a mechanical failure has occurred. Conditions which contributed to a code of this nature being stored should be rectified as quickly as possible.

How Can You Fix The P081B Code?

A diagnostic scanner, a digital volt/ohmmeter (DVOM), and a source of vehicle specific diagnostic information will be required to diagnose a code P081B.

You may use your source of vehicle information to locate a technical service bulletin (TSB) that matches the vehicle year, make, and model; as well as the engine size, code/s stored, and symptoms exhibited. If you find one, it could yield helpful diagnostic information.

Use the scanner (connected to the vehicle diagnostic connector) to retrieve all stored codes and pertinent freeze frame data. It is a good idea to write this information down before clearing the codes then test-drive the vehicle until the PCM either enters readiness mode or the code is reset.

If the PCM enters readiness mode at this time, the code is intermittent and may be much more difficult to diagnose. If this is the case, the conditions which contributed to the code being stored may need to worsen before an accurate diagnosis can be made.

If the code is immediately reset, the next step of your diagnosis will require that you search your vehicle information source for diagnostic flow-charts, connector pin-out charts, connector face views, and component testing procedures/specifications.

Step 1

Use the DVOM to test voltage, ground, and signal output at the appropriate starter disable switch. Typical starter disable switch circuits consist of either battery voltage (when activated) or ground (when deactivated).

Step 2

Use your source of vehicle diagnostic information and the DVOM to test starter disable switches as required. Replace switches that do not test within system parameters.

Step 3

If system switches and circuits are functional, use the DVOM to test starter disable switch circuits to the starter, as well as to the PCM. Disconnect all controllers prior to using the DVOM for testing.

Note:

• Starter disable switch circuit codes are most often attributed to switch failure
• Vehicles with manual transmissions often use multiple starter disable switches (one for the clutch and another for neutral)

Recommended Parts

Below are some recommended auto parts to help you address the trouble code affecting your vehicle and get it running smoothly again:

>>> Twippo 372Pcs Waterproof Wire Connectors Kit
>>> ECU
>>> Autel Scanner MaxiCOM MK808S
>>> KAIWEETS Digital Multimeter

Note: During the purchasing process, please check carefully whether the part you want to buy fits your car!

Reference Sources

P081B Starter Disable Circuit High, OBD-Codes.