P0978: Shift Solenoid C Control Circuit Range/Performance

Range/performance fault in the drive circuit of shift solenoid C. GM's 2007 Allison 1000 table used it for an open SS3 circuit, but only while the commanded gear is not reverse trim, 5th or 6th; the table even prints the label Circuit Low beside an open-circuit test, an apparent typo. FCA lists P0978 among the four codes that the 2014–2016 9-speed transaxle set under old software when the range sensor harness had poor crimps. Ferrari's DCT bulletin uses it for a missing signal from the actuator 4 engage position sensor. Ford and GM six-speeds do not use it. Low/high are P0979/P0980, the current open code P097C.

Symptoms

• MIL or transmission warning on
• Sudden neutral or default gear while driving
• Erratic or missing shifts

Most likely causes

• Intermittent high resistance at crimped harness terminals (FCA 9-speed)
• Open coil of shift solenoid C (Allison-type usage)
• Transmission software that predates the manufacturer's fix
• Faulty driver stage in the transmission control module

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the fluid level and condition according to the manufacturer
2. Compare the reading with other engine data while varying the engine speed.
3. Check the transmission connector
4. Read the data with a transmission-compatible scanner
5. Measure the solenoid valve circuit
6. Leave opening the transmission to a specialized repair shop

Good to know

• Repair difficulty: hard
• It can trigger limp mode.
• It affects emissions.

What each character of P0978 means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 9: Transmission
• 78: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0978?

Drive as little as possible and gently. If the transmission slips or stays in one gear, go slowly to a repair shop or call for a tow truck.

What causes code P0978?

The most common causes are: intermittent high resistance at crimped harness terminals (FCA 9-speed); open coil of shift solenoid C (Allison-type usage); transmission software that predates the manufacturer's fix.

Related codes

• P097CShift Solenoid C Control Circuit/Open
• P0979Shift Solenoid C Control Circuit Low
• P0980Shift Solenoid C Control Circuit High
• P0760Shift Solenoid C
• P0975Shift Solenoid B Control Circuit Range/Performance
• P0981Shift Solenoid D Control Circuit Range/Performance

Sources

• gsi.ext.gm.com: 07 GRP15 Allison 1000
• static.nhtsa.gov: RCMN 16V529 5540
• static.nhtsa.gov: MC 10168599 0001

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.