P0973
Shift Solenoid A Control Circuit LowP0973 is a generic OBD-II powertrain diagnostic trouble code: Shift Solenoid A Control Circuit Low. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0973 means
P0973 is set when the Transmission Control Module (TCM) detects an abnormally low voltage signal on the Shift Solenoid "A" (also referred to as Clutch Pressure Control Solenoid A) control circuit. These solenoids are PWM-driven devices that regulate hydraulic pressure to the clutch packs inside modern multi-speed automatic transmissions, including GM 6L80/6T70, Ford 6R80, ZF 6HP/8HP, and Mercedes 722.9. A "low" circuit fault indicates an open circuit, a short to ground, or an internally open solenoid coil that prevents the TCM driver from delivering the commanded current.
When the fault is confirmed, the TCM disables the solenoid control circuit and typically forces the transmission into a fail-safe or limp-home mode, locking it in a single mid-range gear to allow the vehicle to be driven slowly to a workshop. Without solenoid A functioning, certain gear ratios become unavailable and the torque converter clutch may also be disabled, resulting in excessive engine RPM and elevated transmission fluid temperatures.
Diagnosis must begin with a wiring and connector inspection before condemning the solenoid itself, as rodent damage, chafed harnesses, and corroded connector pins are statistically the most common root causes. Internal solenoid resistance at the transmission connector should measure roughly 10–20 ohms; a reading of zero or infinite ohms confirms the fault source.
Common causes
Most-frequently reported root causes when P0973 is logged.
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1
Open circuit in the wiring harness between the TCM and the transmission due to chafing, rodent damage, or a broken wire.
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2
Short-to-ground on the solenoid control wire, pulling the signal line below the TCM's minimum voltage threshold.
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3
Internally open solenoid coil (broken winding) in Shift Solenoid A, resulting in infinite resistance at the connector.
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4
Corroded, bent, or backed-out terminal pins at the transmission harness connector reducing circuit continuity.
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5
Low or severely degraded transmission fluid causing internal contamination of solenoid hydraulic passages.
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6
Failed TCM output driver rendering the solenoid circuit permanently inactive.
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7
Recent major repair work (radiator, cylinder head) causing a harness to be misrouted and pinched.
Symptoms drivers notice
How to diagnose P0973
A typical diagnostic flow when this code is present.
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1
Connect a scan tool, retrieve all stored DTCs, and record freeze-frame data to establish engine load and speed conditions at fault set.
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2
Inspect the transmission wiring harness from the TCM to the transmission connector for rodent damage, chafing against sharp edges, and heat-damaged insulation.
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3
Check all connector terminals for corrosion, backed-out pins, or moisture intrusion; clean and reseat connections as needed.
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4
With the ignition off and the transmission connector unplugged, measure resistance between the solenoid A control terminals using a DVOM — expect 10–20 ohms; 0 ohms indicates a short, infinite indicates an open coil or broken wire.
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5
Perform a voltage drop test on the supply and ground circuits with the ignition on to confirm the TCM driver is providing the correct operating voltage.
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6
Check transmission fluid level and condition; drain a sample to inspect for burnt odor, dark colour, or metallic debris that could indicate internal solenoid contamination.
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7
If wiring and fluid check out, lower the oil pan, remove and bench-test Solenoid A, replacing it if resistance is out of specification.
Related powertrain codes
Frequently asked questions
Can I drive with a P0973 code active?
The vehicle may still be drivable in limp mode, but continuing to drive long distances is not recommended. Locked in a single gear, the transmission can overheat and suffer accelerated wear. Drive only as far as needed to reach a workshop.
Is P0973 always caused by a bad solenoid?
No. The majority of P0973 cases are traced to wiring faults — chafed harnesses, corroded connector pins, or rodent-damaged wires — rather than solenoid failure itself. Always inspect and test the circuit thoroughly before replacing the solenoid.
Which transmissions commonly set P0973?
P0973 appears frequently on GM 6L80/6T70/8L90 units, Ford 6R80/10R80, ZF 6HP26/8HP45/8HP70 found in BMW and Audi vehicles, and Mercedes-Benz 722.6/722.9 gearboxes. The solenoid designations vary by platform but the circuit fault logic is standardised.
Will clearing the code and re-driving fix a P0973?
Only if the fault was intermittent due to a loose connector or marginal connection. If the underlying wiring damage or solenoid failure is still present, the TCM will re-set P0973 within one drive cycle once the solenoid circuit is re-tested.
Disabling P0973 in software
RaceTune can permanently disable P0973 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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