P0979
Shift Solenoid C Control Circuit Low
Powertrain Transmission Control Shift Solenoid Circuit 🟡 Moderate — Fix within a week
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What This Actually Means
In plain language — no jargon

The transmission control computer detects that Shift Solenoid C isn't receiving enough electrical power to operate properly. It's like a water valve that needs electricity to open, but the power supply is too weak.

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Symptoms You May Notice
3 known symptoms for this code
Transmission stuck in one gear or limp mode
Check Engine Light illuminated
Harsh or delayed gear shifts
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECM monitors the voltage and current supplied to Shift Solenoid C during activation. It compares the measured circuit voltage against expected thresholds to detect low voltage conditions that prevent solenoid operation. If voltage drops below the minimum threshold, the fault is logged.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Solenoid Circuit Voltage 11-14 volts during activation Below 8 volts or open circuit
Solenoid Control Current 0.5-2.0 amps Below 0.3 amps or no current draw
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Battery terminals and connectors
Clean corrosion from battery terminals and inspect transmission control harness connectors for loose or corroded connections.
2
Shift Solenoid C wiring harness
Check the wiring between the ECM and solenoid for breaks, exposed wires, or pinched insulation and repair as needed.
3
Shift Solenoid C replacement
Replace the solenoid if wiring and connections are intact but resistance or continuity tests fail.