P0652 Low Voltage Sensor Reference B Circuit

OBD-II Trouble Code - P0652 - Data Sheet

P0652 - Low voltage in the reference voltage circuit of the sensor "B"

Code P0652 means that a malfunction has been detected in the “B” sensor voltage reference circuit, and this was most likely done by the transmission control module or another control module associated with the system.

What does trouble code P0652 mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code, which means it applies to OBD-II equipped vehicles. Although general, specific repair steps may differ depending on the brand / model.

If your OBD II vehicle has a P0652 stored, it means that the powertrain control module (PCM) has detected a low reference voltage signal for a specific sensor that has been assigned the designation “B”. The sensor in question is usually associated with an automatic transmission, transfer case, or one of the differentials.

A more specific sensor code almost always accompanies this code. P0652 adds that the sensor reference circuit voltage is low. To determine the location (and function) of the sensor for a particular vehicle, consult a trusted vehicle information source (All Data DIY is a great option). I suspect a PCM programming error has occurred if P0652 is stored separately. You will need to diagnose and repair any other sensor codes prior to diagnosing and repairing P0652, but be aware of the low reference voltage.

The sensor in question is supplied with a reference voltage (usually five volts) through a switchable (powered when the switch is on) circuit. There will also be a ground signal. The sensor will be either variable resistance or electromagnetic type and it completes the circuit. The resistance of the sensor should decrease with increasing pressure, temperature or speed, and vice versa. As the sensor resistance changes (depending on conditions), it supplies the PCM with an input voltage signal.

If the input voltage signal received by the PCM is below the programmed limit, P0652 will be stored. A malfunction indicator lamp (MIL) may also be illuminated. Some vehicles will require several driving cycles (in case of failure) for the warning lamp to illuminate. Let the PCM go into readiness mode before assuming a repair is successful. Just remove the code after repair and drive as normal. If the PCM goes into readiness mode, the repair was successful. If the code is cleared, the PCM will not go into standby mode and you know the fault is still there.

Severity and symptoms

The severity of the stored P0652 depends on which sensor circuit is in the low voltage state. Other stored codes must be reviewed before a severity determination can be made.

In addition to the code being stored, a P0652 code has several common symptoms that include an engine that starts to run very rough, engine is difficult to start (or won't start at all), a distinct drop in fuel consumption, engine misfiring, check engine light, and a low vehicle operating power.

Symptoms of a P0652 code may include:

• Inability to switch the transmission between sport and economy modes
• Gear shift malfunctions
• Delay (or lack) of turning on the transmission
• Transmission failure to switch between XNUMXWD and XNUMXWD
• Failure of the transfer case to switch from low to high gear
• Lack of inclusion of the front differential
• Lack of engagement of the front hub
• Incorrect or not working speedometer / odometer

Causes of the P0652 code

Possible causes of this engine code include:

• Bad sensor
• Defective or blown fuses and / or fuses
• Faulty system power relay
• Open circuit and / or connectors
• Internal problems with PCM
• Open or shorted conduction and/or connectors between two or more control modules
• Open or short circuit in wiring and/or connectors in engine control unit input circuit (usually from engine sensors).
• Disconnected or loose ground wires to one of the control modules

Diagnostic and repair procedures

Diagnosing a stored P0652 code will require a diagnostic scanner, a digital volt / ohmmeter (DVOM), and a trusted source of vehicle information (such as All Data DIY). A handheld oscilloscope can also be helpful in making a diagnosis.

First, consult your vehicle information source to determine the location and function of the sensor in question, as it relates to your specific vehicle. Visually inspect the harness and connectors associated with the sensor system. Repair or replace damaged or burnt wiring, connectors, and components as needed. Secondly, connect the scanner to the vehicle diagnostic port and retrieve all stored DTCs and freeze frame data. Make a note of the codes along with the order in which they were stored and any relevant freeze frame data, as this information may be helpful if the code turns out to be intermittent. Now you can go ahead and clean up the code; then test drive the vehicle to make sure it is reset immediately.

If the code resets immediately, use the DVOM to test the reference voltage and ground signals on the sensor in question. Typically you would expect to find five volts and ground at the sensor connector.

Continue testing sensor resistance and continuity levels if voltage and ground signals are present at the sensor connector. Obtain test specifications from your vehicle information source and compare your actual results to them. Sensors that do not meet these specifications should be replaced.

Disconnect all related controllers from the system circuits before testing resistance with the DVOM. Failure to do so could damage the PCM. If the reference voltage is low (at the sensor), use the DVOM to test the circuit resistance and continuity between the sensor and the PCM. Replace open or shorted circuits as necessary. If the sensor in question is a reciprocating electromagnetic sensor, use an oscilloscope to track the data in real time. Focus on crashes and completely open circuits.

Additional diagnostic notes:

• This type of code is usually provided as support for more specific code.
• A stored code P0652 is usually associated with the transmission.

How does a mechanic diagnose a P0652 code?

The mechanic will diagnose the P0652 code using an OBD-II scanner and also run some visual checks. The first step for the mechanic is to examine the freeze frame data and determine when the code first appeared. They should then reset the trouble codes and do a road test to see if that causes the code to reappear.

They will then conduct a visual inspection of the connectors and wiring associated with the "B" circuit. They will look for any disconnected, shorted, or corroded wiring and components, including fuses. If everything is in order, you can proceed to the repair. If not, they should perform any repairs or replacements and then re-test the car to see if the code still occurs. If yes, then you can proceed to the repair.

Common Mistakes When Diagnosing Code P0652

Since this particular code is associated with a wide range of potential problems, it is important to carefully evaluate stored codes along with any symptoms. Often, mechanics treat codes as the cause of the problem, allowing them to make unnecessary repairs.

How serious is the P0652 code?

Code P0652 can cause the vehicle to reach no start state . This can cause the engine to run very rough and uneven, and it can gobble up fuel. The vehicle may have difficulty accelerating or having the power to match the needs of the driver and so this is a very serious issue.

What repairs can fix code P0652?

Unfortunately, the most common P0652 repair is time consuming and requires a lot of diagnostics and troubleshooting:

• First, the mechanic should use a scanner to check the code and then reset the trouble codes before doing a road test and reviewing the data when they return to the store. If P0652 remains, they should do a visual inspection of the wiring. *Mechanic should locate damaged, open, or disconnected wiring related to circuit "B" and then make any necessary repairs.
• This code refers to several drivability sensors, each of which is part of the controller's local network or CAN bus, which must be evaluated using a special scanner. You cannot manually check thousands of pins on the CAN bus, but the scanner will be able to show the operation of the control modules and pin values.
• Using the CAN Scanner to diagnose electrical circuit problems, determine which parts of the "B" circuit need to be repaired or replaced. Perform a repair and recheck with a scanner to ensure the code has been cleared.

Additional comments to consider regarding code P0652

This code refers to a five volt signal from or to multiple engine drivability sensors. Sensors interact directly with control modules that control various vehicle systems. Although it is possible for individual control modules to fail, this is rare. This problem usually occurs due to wiring problems.

Vw tdi P0652 sensor reference voltage

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