What Does P0998 Mean?
The TCM has detected that the shift solenoid 'F' control circuit is reading low, indicating a short to ground in the solenoid circuit or an internally shorted solenoid. When this circuit is low, the TCM cannot properly control the solenoid's duty cycle, leading to incorrect transmission line pressure or shift engagement.
Common Causes
35%
Shift solenoid F internally shorted causing excessive current draw
30%
Wiring short to ground in the solenoid F control circuit
20%
Corroded or water-damaged connector at the transmission case pass-through
15%
TCM solenoid driver circuit failure
Diagnostic Steps
1
Step 1: Disconnect the transmission case connector and measure the resistance of solenoid F. A reading significantly below specification (typically below 5 ohms when spec is 10-25 ohms) confirms an internal short.
2
Step 2: With the connector unplugged from the transmission, check for continuity between the solenoid F control wire and ground at the TCM harness side. No continuity should exist; continuity indicates a harness short.
3
Step 3: Inspect the transmission case pass-through connector for corrosion, moisture, or melted/damaged pins. ATF leaks through the harness can wick into connectors.
4
Step 4: If the solenoid and harness test good, command the solenoid on/off using bidirectional scan tool controls while monitoring current draw. Current should match the commanded duty cycle within specification.
5
Step 5: If all external circuits test good, suspect a failed solenoid driver in the TCM. Verify by measuring the TCM output voltage at the solenoid control pin with KOEO.
Estimated Repair Cost
$200 - $850
Parts + labor, varies by vehicle and location
The TCM has detected that the shift solenoid 'F' control circuit is reading low, indicating a short to ground in the solenoid circuit or an internally shorted solenoid. When this circuit is low, the TCM cannot properly control the solenoid's duty cycle, leading to incorrect transmission line pressur...
The most common cause of P0998 (Shift Solenoid "F" Control Circuit Low) is: Shift solenoid F internally shorted causing excessive current draw
Typical repair costs for P0998 range from $200 to $850, depending on the vehicle, location, and whether you do it yourself or go to a shop.
The transmission may default to limp mode or fail to engage certain gears. Drivability is significantly impacted. Repair before extended driving.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0998 to identify the root cause.
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Quick Info
Category
Powertrain
System
Transmission Shift Control
Difficulty
Type
Generic (SAE)
Recommended Tools
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