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Technical Description of OBD-II Trouble Code
Range/Performance Issue with Sensor Reference Voltage D Circuit
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. This includes vehicles from Ford, Chevrolet, Honda, and others. While it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
If your OBD-II vehicle has a stored P06A9 code, it means that the powertrain control module (PCM) has detected an out of range reference voltage signal or a performance problem with a specific sensor designated as “D”. This sensor is typically associated with the automatic transmission, transfer case, or one of the differentials.
Usually, there will be a more specific sensor code accompanying the P06A9 code. The P06A9 code indicates that the sensor reference circuit voltage is out of range or not performing as expected. To determine the location and function of the “D” sensor for your specific vehicle, consult a reliable source of vehicle information such as AllDataDIY. If the P06A9 code is stored alone, it is possible that a PCM programming error has occurred. Before diagnosing and repairing the P06A9 code, it is necessary to diagnose and repair any other sensor codes. However, keep in mind the range/performance reference voltage condition.
The sensor in question receives reference voltage (typically 5 volts) through a switched circuit that is energized with the key on. There will also be a ground signal. The sensor is either of the variable resistance or electromagnetic type, and it completes the circuit. As pressure, temperature, or speed increases, the sensor resistance should decrease, and vice versa. The changing sensor resistance provides the PCM with an input voltage signal that varies with different conditions.
Here is an example photo of a PCM:
If the input voltage signal received by the PCM is outside the expected parameters, a P06A9 code will be stored. In some cases, a malfunction indicator lamp (MIL) may also illuminate. Some vehicles may require multiple drive cycles with a failure for the MIL to illuminate. It is important to allow the PCM to enter readiness mode before considering a repair successful. After performing the repairs, simply clear the code and drive the vehicle normally. If the PCM enters readiness mode, the repair was successful. If the code is reset, the PCM will not enter readiness mode, indicating that a malfunction still exists.
Severity & Symptoms
The severity of this DTC depends on which sensor circuit is experiencing the abnormal voltage situation. It is necessary to consider other stored codes before determining the severity.
Symptoms of a P06A9 code may include:
Causes
Possible causes for this engine code include:
Diagnostic and Repair Procedures
To diagnose a stored code P06A9, you will need a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable source of vehicle information such as All Data DIY. A portable oscilloscope may also be helpful in the diagnosis.
First, consult your vehicle information source to determine the location and function of the sensor in question for your specific vehicle. Perform a visual inspection of the wiring harnesses and connectors related to the sensor system. Repair or replace any damaged or burned wiring, connectors, and components as necessary. Second, connect the scanner to the vehicle diagnostic port and retrieve all stored trouble codes and freeze frame data. Write down the codes, the order in which they were stored, and any related freeze frame data, as this information may be useful if the code is intermittent. Clear the code and test drive the vehicle to see if it is immediately reset.
If the code is immediately reset, use the DVOM to test the reference voltage and ground signals at the sensor in question. Normally, you would expect to find 5 volts and a ground at the sensor connector.
If the voltage and ground signals are present at the sensor connector, continue by testing the sensor resistance and continuity levels. Compare your actual findings to the testing specifications provided by your vehicle information source. Sensors that do not comply with these specifications should be replaced.
Prior to testing resistance with the DVOM, disconnect all related controllers from the system circuits. Failure to do so could result in PCM damage. If the reference voltage is low at the sensor, use the DVOM to check circuit resistance and continuity between the sensor and the PCM. Replace any open or shorted circuits as necessary. If the sensor in question is electromagnetic with a reciprocating signal, use the oscilloscope to monitor live data and focus on glitches and completely open circuits.
Additional diagnostic notes:
Professional Service
While we always recommend seeking professional mechanical assistance to resolve this issue, if that is not possible, we offer the option to permanently delete this specific DTC. All other codes will continue to function. If you are interested in this option, please upload your ECU file to our portal.
