Fault code P2745 – intermediate shaft speed sensor “B” circuit malfunction

Fault code P2745 is called “Intermediate Shaft Speed (ISS) Sensor “B” Circuit Malfunction” 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 P2745

Diagnostic fault code P2745 indicates a fault in the intermediate shaft speed sensor (ISS) “B” circuit. Without an accurate output speed signal, the Transmission Control Module (TCM) cannot shift gears properly, so this code is set.

Fault code P2745 – intermediate shaft speed sensor

The intermediate shaft, helps distribute rotational force from the input drive to the output shaft inside the transmission. The speed of the intermediate shaft depends on what gear you are in.

In a manual transmission, the gear selector determines this, so there is no need to control the speed of the intermediate shaft. In an automatic transmission, the gear you’re in is determined by the transmission control module (TCM). It also uses several sensor inputs that contribute to a smooth and efficient gear shift.

When the transmission control module (TCM) detects a malfunction, the PCM/ECM can substitute values based on other sensors to determine shift timing. This adjusts the torque converter and pressure when ISS sensor information is not available.

Error code P2745 is set when the Transmission Control Module (TCM) monitors a general fault in the speed sensor “B” or its circuit. Without the correct signal from the intermediate shaft speed sensor, the transmission cannot provide an optimal shift strategy.

The intermediate shaft speed should gradually increase until the desired shift point is reached. If the sensor is defective, this does not happen, so it will not be possible to determine the gear shift strategy.

Symptoms of vehicle malfunctions

The main signal that an error P2745 has occurred is the Malfunction Indicator Lamp (MIL) is also known as the CheckEngine Light.

It can also be warning signs such as:

  1. The “Check engine” control lamp on the control panel will light up (the code will be stored as a fault).
  2. Other related trouble codes may also be present.
  3. Inoperative speedometer or tachometer, or malfunction.
  4. Hard shifting of gears.
  5. Problems with gear shifting.
  6. Engine not accelerating well.
  7. Ignition jerking/missing at idle or under load.
  8. Engine stalls or fails to start.
  9. Reduced power output of the engine.
  10. Increased fuel consumption.

Error P2745 is quite serious, as the conditions that led to its persistence may cause damage to the transmission.

Factors that can cause this error code

The error code P2745 can mean that one or more of the following problems have occurred:

  • Intermediate shaft speed sensor (ISS) is defective or damaged.
  • Output shaft speed sensor has failed.
  • Faulty input shaft speed sensor.
  • Transmission shift solenoid valve is not working properly.
  • Open, shorted wiring or connectors in the circuits of the listed sensors.
  • Contaminated or insufficient transmission fluid.
  • Sometimes the cause is a faulty PCM module.

How to fix or reset OBD-2 code P2745

Some suggested steps for troubleshooting and fix the error code P2745:

  1. Read all saved errors with an OBD-II scanner.
  2. Clear the errors and do a test drive to see if error P2745 appears again.
  3. If the code appears again, inspect the wires and connectors for damage.
  4. Test the intermediate shaft speed sensor (ISS) circuit, if there is a problem, replace the faulty sensor.
  5. Inspect the electrical wiring and connections of the associated sensors.
  6. If necessary, flash or replace the PCM.

Diagnose and repair of problems

It’s a good idea to first look up the technical service bulletins (TSB) for your specific make of car with error P2745. If the problem is already described, following the instructions can save you time and money in diagnosing and correcting the problem.

Visually inspect all wiring and connectors leading to the intermediate shaft speed sensor (ISS). Look carefully for abrasions, exposed wires, or broken wires. Also look for melted or otherwise damaged areas. Repair if necessary.

Electrical wiring

Inspect the wiring harness for loose connections, loose wires, or dirty terminals. Disconnect all connections from the vehicle wiring harness, intermediate shaft speed sensor, and PCM/ECM unit.

Using a multimeter on an ohm scale, check for excessive resistance. If the resistance is very high, trace the wiring through the circuit between each connector to determine the cause.

If the resistance indicates over the limit, look for broken or damaged wiring. Check for a ground fault in the wiring harness sections by moving the positive or negative lead to a good ground.

If resistance is present, there may be a short to the ground. The wiring harness should be checked for damaged wiring or sections that may be frayed from touching the vehicle chassis.

Faulty wiring can quite often cause error P2745.

Intermediate shaft speed sensor

A common problem with the intermediate shaft speed sensor is contamination. Therefore, after removing the sensor, the best option is to clean it. You can use a clean rag and brake cleaner for this.

Check the wiring harness for possible signs of damaged wiring or loose connections. Measure the resistance by removing the connector and using a digital multimeter set to the ohm scale. If the resistance is out of range or above the limit, replace the sensor.

Check for power to the sensor and PCM harness connector using the factory wiring diagram. If no power is detected, the sensor will need to be replaced.

Depending on the model of vehicle, the voltage reading should be 12 volts or a 5 volt reference voltage. If the voltage does not meet the specifications, you may suspect a short circuit to the ground.

Also do not rule out a faulty PCM / ECM or a problem in the wiring between the transmission and the PCM / ECM.

On which vehicles does this problem occur most frequently

Fault code P2745 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • BMW
  • Chevrolet
  • Chrysler
  • Dodge
  • Ferrari
  • Ford
  • Jeep
  • Lexus
  • Mazda
  • Mercedes-Benz
  • Mini (Cooper)
  • Toyota
  • Volkswagen

Fault code P2745 can sometimes be found with other errors. The most common are the following: P2746, P2747, P2748.

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