TCM Engine Speed Output Circuit
P0737 indicates the transmission control module (TCM) has detected a malfunction or open circuit in the engine speed output signal pathway. This code sets when the TCM cannot properly communicate engine speed data needed for transmission shift timing and torque converter control.
What You Might Notice
- Hard or delayed gear shifts
- Decreased fuel economy
- Engine stalling or bucking at low speeds
- Inaccurate speedometer reading
- Reduced throttle response
- Difficulty starting or no-start condition
Most Common Causes
- 1
Defective Engine Speed Sensor
The crankshaft or camshaft position sensor is malfunctioning or has failed, preventing accurate engine speed signals from reaching the TCM.
- 2
Wiring or Connector Issues
Damaged, corroded, or loose wiring and connectors in the engine speed sensor circuit are blocking signal transmission to the TCM.
- 3
TCM Malfunction
The transmission control module itself may have an internal fault or failed input circuit preventing proper speed signal reception.
- 4
Engine Control Module (ECM) Communication Failure
The ECM is not properly transmitting engine speed data to the TCM due to software or communication bus issues.
How to Diagnose It
- 1
Check Defective Engine Speed Sensor — The crankshaft or camshaft position sensor is malfunctioning or has failed, preventing accurate engine speed signals from reaching the TCM.
- 2
Check Wiring or Connector Issues — Damaged, corroded, or loose wiring and connectors in the engine speed sensor circuit are blocking signal transmission to the TCM.
- 3
Check TCM Malfunction — The transmission control module itself may have an internal fault or failed input circuit preventing proper speed signal reception.
- 4
Check Engine Control Module (ECM) Communication Failure — The ECM is not properly transmitting engine speed data to the TCM due to software or communication bus issues.
How to Fix It
- 1
Test and Replace Engine Speed Sensor
Use a multimeter or scope to verify the engine speed sensor is generating proper voltage signals. If faulty, replace the sensor and clear the code to verify resolution.
- 2
Inspect and Repair Wiring Harness
Visually inspect all wiring and connectors between the engine speed sensor and TCM for corrosion, damage, or loose connections. Repair or replace damaged wiring and reseat connectors firmly.
- 3
Check TCM Connector and Pins
Inspect the TCM connector pins for corrosion or damage. Clean contacts with electrical cleaner and ensure the connector is fully seated and locked in place.
- 4
Reprogram or Replace TCM
If wiring and sensors check good, have the TCM reprogrammed with updated software or replaced if internal failure is confirmed through diagnostic testing.
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