P0976
Shift Solenoid B Control Circuit LowP0976 is a generic OBD-II powertrain diagnostic trouble code: Shift Solenoid B 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 P0976 means
P0976 is set when the Transmission Control Module (TCM) detects a voltage reading below the acceptable minimum on the Shift Solenoid "B" (Clutch Pressure Control Solenoid B) control circuit. Like Solenoid A, Solenoid B is a PWM-driven hydraulic actuator responsible for applying and releasing specific clutch packs or bands in the automatic transmission; it is a fundamental element of adaptive shift control in units such as the GM 6L80, Ford 6R80, ZF 8HP, and Denso-built Toyota/Lexus automatics.
A "low" condition on Solenoid B means the TCM's driver circuit is not seeing the expected current return — indicating an open circuit, a wire broken to ground, or an internally open solenoid winding. When the fault is detected the TCM disables the solenoid B control output and typically triggers limp mode to protect the transmission from uncontrolled clutch-pack engagement. Without Solenoid B operating, the gearbox cannot complete the full shift range and may be unable to reach 4th gear and above.
Diagnosis follows the same methodology as P0973: harness inspection first, connector condition second, and solenoid resistance measurement third. Solenoid B is often located adjacent to Solenoid A in the valve body, and harness damage affecting one solenoid frequently affects both, so it is common to see P0973 and P0976 set together on the same vehicle.
Common causes
Most-frequently reported root causes when P0976 is logged.
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1
Open circuit in the harness between the TCM and Solenoid B from a broken wire, excessive resistance, or rodent damage.
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2
Short-to-ground on the control wire pulling the signal below the TCM's minimum current threshold.
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3
Internally open solenoid coil in Shift Solenoid B, measurable as infinite resistance at the connector.
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4
Corroded, backed-out, or broken terminal pins at the transmission multi-pin connector.
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5
Low or severely degraded transmission fluid causing valve body hydraulic passages to restrict solenoid movement.
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6
Harness chafing where the transmission loom passes over the transmission case or chassis crossmember.
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7
Simultaneous harness damage affecting both Solenoid A and Solenoid B if P0973 is also present.
Symptoms drivers notice
How to diagnose P0976
A typical diagnostic flow when this code is present.
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1
Scan all DTCs and record freeze-frame data; note if P0973 is also stored, as concurrent codes suggest a shared harness fault rather than a single solenoid failure.
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2
Inspect the entire transmission wiring harness from the TCM to the transmission connector for rodent damage, chafing, heat damage, or pinching at routing clips.
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3
Examine the transmission harness connector for corroded, bent, or unseated terminals and for evidence of moisture or fluid ingression.
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4
With the harness connector unplugged and ignition off, measure resistance between the Solenoid B terminals using a DVOM; normal range is 10–20 ohms; open or zero reading confirms the fault location.
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5
Perform a continuity check along the harness wire from the TCM pin to the transmission connector pin to isolate any open or high-resistance segment.
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6
Check and service transmission fluid — drain a sample and inspect for contamination, burnt odour, or metallic particles.
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7
If harness and fluid checks pass, remove the transmission oil pan, access Solenoid B, and bench-test resistance directly at the solenoid body before replacing it.
Related powertrain codes
Frequently asked questions
What gears are lost when Solenoid B fails?
The specific gears affected depend on the transmission design and which clutch packs Solenoid B controls. In most 6- and 8-speed units it controls a mid-range clutch, so 4th gear and above become unavailable. The TCM typically locks the unit in 2nd or 3rd gear as a fail-safe.
Why do P0976 and P0973 appear together?
Both solenoids share a common wiring harness routed from the TCM to the transmission connector. Rodent damage, a pinched loom, or a corroded multi-pin connector can affect several solenoid circuits simultaneously. If both codes are present, focus the diagnosis on the shared harness segment and connector before testing individual solenoids.
Can bad transmission fluid cause P0976?
Contaminated fluid can cause solenoid valve sticking due to debris in the hydraulic passages, which may indirectly contribute to circuit faults and poor solenoid response. However, P0976 is primarily an electrical fault code. Fluid condition should be checked and corrected as part of the service, but is rarely the sole cause of the circuit low fault.
Is it safe to drive until a repair appointment?
The vehicle is usually still drivable in limp mode for short distances at reduced speed. Prolonged driving in limp mode raises transmission fluid temperature significantly, accelerating wear. Avoid highway speeds and schedule the repair promptly to prevent escalating damage.
Disabling P0976 in software
RaceTune can permanently disable P0976 — 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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