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P0974 OBD-II Trouble Code: Shift Solenoid A Control Circuit High

diagnostic check engine light

P0974 code definition

The P0974 code is generic powertrain code related to the transmission, including pressure faults and sensor failures. In this case, the engine control module (ECM) has detected a fault with a high voltage reading from the shift solenoid A control circuit.

What the P0974 code means

Solenoid valves helps the automatic transmission change gears and are controlled by the transmission control module, which could be separate from the ECM in some vehicle makes and models.

A code P0974 will be stored when the shift solenoid A, or No. 1, is “OFF” and a status continues for 0.5 seconds with the automatic transmission ECM terminal monitor signal is on for one drive cycle.

What causes the P0974 code?

Several problems may cause a P0974 code including:

  • Low transmission fluid
  • Dirty or contaminated transmission fluid
  • Damaged or defective wiring
  • Open or shorted wiring
  • Damaged or defective shift solenoid A
  • Damaged or defective ECM (rare)

What are the symptoms of the P0974 code?

Symptoms of a P0974 code may include:

  • Check engine or warning light may illuminate
  • Vehicle may not shift into one or more gears in “D” mode
  • Acceleration may be slow
  • Vehicle may shift harshly
  • Decreased fuel economy

How does a mechanic diagnose the P0974 code?

A mechanic may use several methods to diagnose a P0974 trouble code, including:

  • Utilize an OBD-II scanner to check for a stored P0974 trouble code
  • Check transmission fluid level
  • Check transmission fluid quality
  • If transmission fluid quality is degraded or burned, check transmission pan for clutch debris or other contaminants, which could signal a larger transmission-related problem
  • Visually inspect wiring for any damage, corrosion, or wear
  • Check the wiring harness for damage
  • Check that all connectors are properly connected and that there are no bent pins
  • Perform a circuit check, including checking resistance between terminals or terminal and body ground, depending on vehicle make and model
  • Check harness for continuity
  • Check the shift solenoid for damage

Common mistakes when diagnosing the P0974 code

As with any transmission-related fault or trouble code, it is possible that the cause is low or dirty transmission fluid. It is recommended to check transmission fluid levels and quality, filling or flushing as needed, before performing any additional repairs.

How serious is the P0974 code?

Because a vehicle’s safe driving operation most likely will be impacted due to faults that store a P0974 code, this code is considered a potentially serious code. When this code appears, it is recommended to immediately take your vehicle to your local service center or mechanic for repair and diagnosis.

What repairs can fix the P0974 code?

Several repairs can fix a P0974 trouble code and include:

  • Fill transmission fluid to manufacturer recommended levels
  • Perform a transmission fluid flush if needed
  • Repair or replace damaged or defective wiring harness
  • Repair or replace damaged or defective connectors
  • Repair or replace damaged or defective shift solenoid A
  • Repair or replace damaged or defective ECM (rare)
  • Clear all codes, test-drive the vehicle, and rescan to see if any codes reappear

Additional comments related to code P0974

Incorrect repairs on the radiator or cylinder head can cause a P0974 trouble code due to misrouted harnesses or other errors.

In addition, this code is common on vehicles that have been stored for periods of time and have animals taking residence in the vehicle’s engine compartment and gnawing on wires.

Need help with a P0974 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
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