P0978 OBD Error Code: Problem & Solutions

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Is the shift solenoid ‘C’ broken? Is the electrical connection poor? Then you’re more likely to experience the P0978 error code in your vehicle. The shift solenoids are used by the TCM to monitor the hydraulic pressure. This is required to apply clutch packs in the transmission which offers several gear ratios. This, in turn, will make your vehicle move efficiently down the road. If the pressure control solenoid malfunctions, then the P0978 error is set.

The gear shift receives a command from ECM, to turn the shift solenoid valves to ON/OFF position. The check engine light will be illuminated if there is an opening or short circuit in the shift solenoid which is identified by the ECM and the trouble code is stored. The remaining shift solenoid valve will be turned to good condition ON/OFF while the ECM completes the failsafe function.

What causes this problem with the Shift Solenoid "C" Control Circuit Range/ Performance?

• Shift solenoid ‘C’ is defective.
• An opening or short circuit in the shift solenoid ‘C’ harness.
• Electrical connection is weak in the shift solenoid ‘C’.

1. Engine Control Module – Are you looking for a replacement for your faulty ECM? Find them at Parts Avatar at the best prices.
2. Transmission Fluid – Replacing the dirty transmission fluid, can help you to get rid of the P0978 error code.
3. Transmission Control Module – Defective TCM must be repaired or changed immediately for the system to function normally.
4. Connector – Are the connectors broken or damaged? Find the right replacement at best prices online from Parts Avatar.
5. Transmission shift solenoid -  This component has to be damage free so that the P0978 error code can be avoided from getting stored.

Interested in knowing the symptoms to OBD code P0978? If yes, then you have arrived at the right place. We at PartsAvatar have listed out few common symptoms associated with this fuel injector problem.

Common Symptoms

The CEL will illuminate if the P0978 error is set. As the TCM is unable to find if the SSC is properly functioning, it will reach failsafe operation, by limiting some functionalities like self-learning and adaptive controls. Few gears may be locked by the transmission which is associated with SSC or will restrict the bound range. You will see slow operation or great revving. The transmission will function throughout its full range of gears if the SSC is being used for torque converter lockup or to dampen the rough shifts by the pressure regulator. When this happens, you will notice a rough shift or the suffering of fuel economy.

It is very important to fix the fault code P0978. So here are some ways with which you can correct this issue:

• Replacing the shift solenoid ‘C’.
• The opening or short circuit in shift solenoid ‘C’ must be repaired.

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It is essential to diagnose this fault code. Here are some steps which a mechanic should follow for diagnosing the problem that triggered a P0978 code to be stored:

• P0978 error is mainly related to the performance of shift solenoid C which can contribute to a defective sensor, wire problem and ECM/TCM issue. A vehicle specific wire diagram and DVOM will be needed to correctly diagnose this issue to test the resistance and continuity for SSC and the wires.
• Inspecting the wire harness - Electrical problems may arise due to wire issue or bad connections. See which module communicates with the SSC with the help of a wiring diagram. Identify the wire harness from module to transmission, by checking for broken wires, erosions, and weak connections. Make sure that the lock tab of each connector is correctly seated or weak connection could exist, setting an error code for the performance SSC in the module.
• Once you make sure that the wire is in good condition, check every connector in the wire harness. Check if the pins or terminals or eroded and if there are presence of moisture in the connector, defective or molded pins, or if the connectors are dirty. Any damage inside the connector must be fixed correctly making sure that the connector is correctly positioned and protected with lock tab.
• Using the DVOM inspect for continuity at the TCM harness. Now you have to find the signal circuit by disconnecting the connector from the TCM with the help of vehicle specific diagram.
• Again use the DVOM and check for continuity in the chassis ground. The continuity must not be present. If you find it, check for a short circuit to the ground.
• Shake the wire harness connectors together with the wire and see if there are any fluctuations in the continuity which shows an erratic connection. In a similar way, the ground circuit along with chassis ground must be tested. If you don’t find the continuity, carefully look for breaks in the SSC ground circuit.

Common Mistakes When Diagnosing The P0978 Code

• Faulty TCM.
• Low-level fluid in the transmission.
• Defective transmission shift solenoid.
• Problematic wires.