OBD-II Code P0974 — What It Means & How to Fix It

What Does This Error Mean?

P0974 means Shift Solenoid A Control Circuit is High. A high circuit condition means the TCM detects higher voltage than expected at the solenoid A control wire. This is typically caused by an open circuit or a short to the positive supply voltage (B+). You may experience no upshifts into certain gears, harsh shifts, or limp mode activation.

Affected Models

All automatic transmission vehicles 1996 and newer
Common in GM vehicles with 4L60E, 4L80E, 6L80, and 6T40 transmissions
Common in Ford vehicles with 4R70W and 6R80 transmissions
Common in Dodge and Chrysler vehicles with 45RFE and 68RFE transmissions

Common Causes

Open circuit in the solenoid A control wiring between TCM and solenoid
Short to battery positive voltage (B+) in the solenoid A control wire
Failed shift solenoid A with an open coil winding
Damaged or disconnected external transmission harness connector
Faulty TCM output driver providing incorrect high-voltage output

How to Fix It

Check the external transmission harness connector first. An unplugged or damaged connector immediately creates a high or open circuit condition.

Visually inspect the connector at the side of the transmission — a loose or corroded connector is the simplest fix.
With the connector unplugged, measure solenoid A resistance from the external harness side. An open reading (infinite ohms) confirms solenoid failure or internal harness break.

If the reading is normal from the external side but the code persists, suspect wiring between the TCM and the external connector.
Check the solenoid A control wire for a short to B+ voltage. With the connector unplugged, measure between the control wire and ground. Anything above 0.5V indicates a B+ short.

A B+ short on the control wire can damage the TCM output driver if not corrected promptly.
Inspect the internal harness for open circuits at the solenoid connector inside the transmission pan.

On 4L60E transmissions, open circuits in the internal harness commonly occur at the crimp connections near the solenoid connectors.
Replace the failed solenoid or repair the wiring. Reinstall the pan with fresh ATF and filter. Clear codes and confirm correct shifts.

Monitor solenoid A activation on a scan tool during a test drive to confirm the circuit is responding normally.

When to Call a Professional

Solenoid replacement with fluid service costs $250 to $550. Wiring harness repair costs $150 to $400. TCM replacement and programming runs $400 to $800. Always perform a full wiring inspection before replacing the TCM.

Frequently Asked Questions

What is the difference between P0973 and P0974?

P0973 is a circuit LOW code — the voltage is lower than expected (short to ground). P0974 is a circuit HIGH code — the voltage is higher than expected (open circuit or short to power). Both affect solenoid A but point to different types of electrical faults.

Will P0974 cause limp mode?

Yes — most TCMs enter limp mode when a primary shift solenoid circuit is high or open. The transmission typically locks into 2nd or 3rd gear. This is a protective measure to prevent further internal damage.

Can a B+ short damage my TCM?

Yes — a short to battery voltage on a control output can burn out the TCM output driver. Fix wiring faults quickly. If the TCM driver is already damaged, it may set codes even after the wiring is repaired.