OBD-II Generic Error Code P0979: How to Fix It
Hard 2-4 hours Medium Severity
Verified July 2026
- Error Code
- P0979
- Brand
- OBD-II Generic
- Product Type
- automotive
- Severity
- Medium
- DIY Difficulty
- Hard
- Estimated Fix Time
- 2-4 hours
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Tools You'll Need
- OBD2 diagnostic scanner
- Digital multimeter
- Basic socket set (metric and standard)
- Ratchet and extension set
- Torque wrench
- Transmission fluid drain pan
- Floor jack and jack stands
- Electrical contact cleaner
- Dielectric grease
- Vehicle-specific wiring diagram
- Back-probe test leads
How to Fix Error Code P0979
-
Confirm the Code with an OBD2 Scanner
Do not ignore additional transmission-related codes. Multiple codes together can indicate a broader electrical or hydraulic failure requiring professional diagnosis. -
Inspect the Transmission Wiring Harness
Always disconnect the negative battery terminal before handling transmission wiring to prevent accidental shorts or electrical damage. -
Check and Clean the Solenoid Connector
Never use water or general-purpose cleaners on electrical connectors. Use only approved electrical contact cleaner. -
Test the Shift Solenoid C Resistance
Perform this test with the engine OFF and the battery disconnected to avoid damaging the multimeter or causing an electrical short. -
Test the Circuit Voltage at the TCM
Use a back-probe adapter or carefully insert a thin test lead into the connector without spreading the terminal pins, which can cause a poor connection. -
Check Transmission Fluid Level and Condition
Using the wrong type of transmission fluid can seriously damage your transmission. Always check your owner's manual or the transmission dipstick for the required fluid specification. -
Replace the Shift Solenoid C (if faulty)
This step involves opening the transmission pan. Work on a level surface, have sufficient drain pans ready, and ensure the vehicle is safely secured on jack stands. Never work under a vehicle supported only by a floor jack. -
Inspect or Replace the TCM (if wiring and solenoid are both good)
TCM replacement often requires vehicle-specific programming. An incorrectly programmed or incompatible TCM can cause additional transmission faults. This step is best handled by a professional.
Parts You May Need
Transmission Shift Solenoid C
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Transmission Solenoid Pack
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Transmission Filter
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Transmission Pan Gasket
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Automatic Transmission Fluid (ATF)
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Transmission Wiring Harness (internal or external)
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Transmission Shift Solenoid C
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Transmission Solenoid Pack
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Transmission Filter
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Transmission Pan Gasket
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Automatic Transmission Fluid (ATF)
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Transmission Wiring Harness (internal or external)
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When to Call a Professional
You should call a professional transmission technician or dealership if: the code returns after replacing the solenoid and flushing the fluid; you find extensive wiring harness damage that requires significant repair; your vehicle requires TCM reprogramming after replacement; your vehicle is in full limp mode and cannot shift safely; or you are not comfortable working under the vehicle or inside the transmission pan. Transmission repairs can be complex and costly if done incorrectly, so professional help is strongly recommended if you are unsure at any step.Frequently Asked Questions
Can I drive my car with a P0979 code?
You can drive short distances with P0979 active, but it is not recommended for extended driving. The fault can cause harsh shifting, slipping, or cause the transmission to enter limp mode, which locks it into a single gear for self-protection. Continued driving without addressing the issue can lead to greater transmission damage and a more expensive repair.
What causes a P0979 shift solenoid high circuit code?
The most common causes include a faulty or shorted Shift Solenoid C, damaged or corroded wiring and connectors in the solenoid circuit, low or contaminated transmission fluid affecting solenoid operation, a defective transmission control module (TCM), or an internal short to voltage in the wiring harness between the TCM and solenoid.
How much does it cost to fix a P0979 code?
The repair cost depends on the root cause. Cleaning a corroded connector may cost nothing beyond your time. Replacing a transmission shift solenoid typically costs between $150 and $400 in parts and labor at an independent shop. If the TCM needs replacement and programming, costs can range from $500 to over $1,200 depending on the vehicle. A transmission fluid service costs approximately $100 to $250.
Will a P0979 code clear itself?
No, P0979 will not permanently clear itself. While the check engine light may temporarily go off if the fault is intermittent, the underlying cause will remain and the code will return. You need to diagnose and repair the root cause, then clear the code using an OBD2 scanner to confirm the fix.
Is P0979 the same on all vehicles?
The definition of P0979 as 'Shift Solenoid C Control Circuit High' is standardized across OBD-II compliant vehicles (1996 and newer). However, the exact location of Shift Solenoid C, the resistance specification, and the repair procedure can vary significantly between makes and models. Always consult a vehicle-specific service manual or wiring diagram for accurate repair information.