OBD-II Code P0973 — What It Means & How to Fix It

What Does This Error Mean?

P0973 means Shift Solenoid A Control Circuit is Low. A low circuit condition means the TCM is detecting lower voltage than expected at the shift solenoid A control wire. This usually indicates a short to ground in the wiring harness or a solenoid with an internal short. You may experience incorrect shifts, no shift into certain gears, harsh engagement, or limp mode.

Affected Models

All automatic transmission vehicles 1996 and newer
Common in GM vehicles with 4L60E, 4L80E, and 6L80 transmissions
Common in Ford vehicles with 4R70W and 5R55 transmissions
Common in Toyota vehicles with A340 and A750 transmissions

Common Causes

Shorted shift solenoid A coil creating a low-resistance path to ground
Short to ground in the solenoid A control wire in the external wiring harness
Short to ground in the internal transmission harness near the solenoid connector
Moisture or fluid intrusion into the external transmission harness connector
Faulty TCM output driver shorting the control circuit internally

How to Fix It

Disconnect the external transmission harness connector. Measure resistance between the solenoid A control wire and ground.

A reading close to zero ohms (short to ground) confirms a wiring or solenoid short. Normal open-circuit resistance should be much higher.
With the external connector still disconnected, reconnect and check whether the short is in the harness between the TCM and the connector, or inside the transmission.

If the short disappears when the transmission connector is unplugged, the short is inside the transmission on the internal harness or solenoid.
If the short is in the internal harness or solenoid, drop the transmission pan and inspect the internal harness and solenoid A connector.

On the 4L60E, the internal harness frequently develops shorts near the connector where the harness bends under the valve body.
Test solenoid A resistance directly at the solenoid terminals (with the solenoid connector unplugged from the harness). If resistance is near zero, the solenoid itself is shorted — replace it.

A shorted solenoid coil reads 0 to 2 ohms rather than the normal 10 to 30 ohm spec.
Replace the shorted solenoid or repair the damaged wiring. Reinstall with fresh fluid and filter, clear codes, and verify correct shift operation.

After repairs, use a scan tool to verify solenoid A commands and monitor that the circuit voltage returns to normal operating levels.

When to Call a Professional

Solenoid replacement with fluid service costs $250 to $550. Internal harness replacement adds $100 to $300. External harness repair is $150 to $400. TCM replacement if the driver is shorted costs $400 to $800 plus programming.

Frequently Asked Questions

What does a low circuit mean?

A low circuit means the TCM is seeing lower voltage than expected. This is usually caused by a short to ground — somewhere the wire is touching metal and draining voltage. Think of it like a hose with a hole — pressure drops before it reaches the end.

Can P0973 damage my TCM?

Potentially — a persistent short to ground can burn out the TCM output driver over time. The faster you fix the wiring or solenoid short, the less risk of TCM damage. Repair it promptly.

Is P0973 the same as P0750?

Related, but different. P0750 means solenoid A has a general malfunction (functional fault). P0973 specifically means the control circuit is shorted low. P0973 is an electrical diagnosis code — it tells you the type of fault, not just that a fault exists.