P0737: TCM Engine Speed Output Circuit

What it means

A circuit fault on the engine speed value the TCM sends to other modules (rev counter, hybrid module).

At a glance

• Usually lights the check-engine light

How it works

The TCM provides an engine-speed signal to other vehicle modules over an output circuit. P0737 indicates a fault in that engine-speed output circuit, so receiving modules may not get a usable signal even if the engine itself runs normally.

Common causes

Most likely first.

1. Open or short in the TCM engine speed output wiring
2. Poor connector contact
3. Fault in the TCM output circuit
4. Low or unstable TCM power or ground

Symptoms

• Check engine or transmission warning light on
• Harsh, delayed, or missing shifts
• Possible limp mode (locked in one gear)
• Slipping or shuddering during gear changes

How to diagnose it

1. Record freeze-frame data and scan all modules for related communication or engine-speed signal codes to identify which systems lost the TCM output.
2. Check live engine-speed data in the engine controller and TCM to see whether the source reading is present and consistent.
3. Inspect the TCM connector and engine-speed output wiring for loose connections, corrosion, water intrusion, or damaged insulation.
4. Check TCM power and ground connections for stability, since a poor supply can disrupt the output signal.
5. Test output-circuit continuity and shorts using the wiring diagram and manufacturer's specification, then assess the TCM output stage if the wiring and supply are sound.

Common fixes

• Reconnect or clean a loose or corroded TCM connector as appropriate.
• Repair an open or short in the TCM engine-speed output wiring.
• Repair an unstable TCM power or ground connection.
• Replace the TCM only if circuit testing confirms an internal output fault and required setup is completed.

Can I keep driving?

If the transmission shifts normally and no other warning or drivability problem is present, a short trip to a repair location may be reasonable, but avoid towing or hard driving. If shifting becomes harsh or the vehicle enters limp mode, stop driving when safe because loss of the signal can affect other modules' control.