P128D Code:

OBD-II Diagnostic Powertrain (P) Trouble Code

Possible Cause

By far the most common cause of thisP128Dcode is from worn or defective transmission shifter components. Other causes may include a defective range sensor, open, shorted, corroded, or otherwise damaged wiring and/or electrical connectors.

Common Symptoms

  1. If the numbers are incorrectly entered, this type of code will be the result
  2. Test the wiring and connectors at the fuel shutoff valve to make sure that voltage and ground readings are near battery voltage
  3. This signal is systematically forwarded to affected control modules that utilize the data to accomplish various other tasks
  4. The sensor is of the electro magnetic design and uses a reluctor ring (or a specialized set of splines) on the input shaft as reference points

Similar Problems

Fuel And Air Metering
TP Sensor Learn Not Complete
TFP Valve Position Switch-Drive Without Drive Ratio

P128D Troubleshooting

If this is the case with the code, you will be hearing very loud noises, like explosions, from the rear of the vehicle upon acceleration. Firstly check the carburetor to ensure that the fuel and air combination are properly balanced. If these settings are correct, then thoroughly inspect the distributor cap for any cracks or hairline splits, as this can produce a backfire. Move on to the spark plugs and ensure that they are clean and undamaged and inspect the engine gaskets for any sign of damage, as they are responsible for ensuring the correct gas exchange within the engine. P128D OBD2 reports a sensor fault, replacement of the sensor is unlikely to resolve the underlying problem. The fault is most likely to be caused by the systems that the sensor is monitoring, but might even be caused by the wiring to the sensor itself.

How to turn off P128D check engine light ?

There are two ways to turn off the check engine light:

A repair technician can do so once repairs have been made.
The OBD II can automatically turn it off when it fails to detect the problem after several diagnostic cycles.

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