Technical Description of OBD-II Trouble Code
Issue with TCM Engine Speed Output Circuit
What does that signify?
This is a generic diagnostic trouble code (DTC) that applies to OBD-II vehicles. It can be found in various vehicle makes such as Dodge, Chevrolet, Honda, Toyota, Hyundai, Jaguar, etc. While the steps for repair may vary depending on the year, make, model, and powertrain configuration, the TCM (Transmission Control Module) functions similarly to the ECM (Engine Control Module) by monitoring, controlling, and regulating the transmission’s functions.
The TCM, along with the ECM, uses sensors, switches, and an Engine Speed Sensor (ESS) to monitor, control, and regulate the drivability of the transmission. The ESS, also known as the CKP (Crankshaft Position Sensor) or OSS (Output Speed Sensor), measures the speed of the engine using a hall effect type sensor that detects notches in the flywheel. It is crucial for the ECM and TCM to have accurate readings from the ESS as it affects shift points, speed, and overall drivability.
When the ECM detects one or multiple conditions outside the specific electrical range of the Engine Speed Sensor or its circuit, it activates the P0737 code and associated codes. While this code is usually related to electrical issues, mechanical problems can also trigger it, although they are less common.
The P0737 code indicates a malfunction or open circuit within the Engine Speed output circuit(s) and is considered to have low severity. However, prolonged use with this fault can lead to potential issues in the long run, so it is important to monitor and address it accordingly.
Some symptoms of the P0737 code may include hard shifts, a drop in fuel mileage, difficulty starting the engine, low speed, engine stalling or bucking, an inaccurate speedometer, and reduced throttle response.
Common causes of the P0737 code include a defective Engine Speed Sensor (ESS), defective ECM (Engine Control Module), defective TCM (Transmission Control Module), wiring issues, a dirty pickup on the ESS, or connector problems.
When troubleshooting the P0737 code, it is recommended to check for technical service bulletins (TSBs) specific to your vehicle, as they may provide known fixes that can save time and money during diagnosis.
Some tools that may be needed for diagnosing or repairing engine speed output circuits and systems include an OBD code reader, multimeter, basic socket set, basic ratchet and wrench sets, basic screwdriver set, battery terminal cleaner, and a service manual.
It is important to follow safety tips such as letting the engine cool, chalking the wheels, and wearing personal protective equipment (PPE) when working on the vehicle.
Basic troubleshooting steps for the P0737 code include testing the Engine Speed Sensor (ESS) for desired electrical values, checking the automatic transmission fluid level and condition, inspecting the wiring for any damage or chafing, cleaning the sensor to remove debris, and inspecting the TCM for signs of corrosion, damage, or defects.
