Transmission Fluid Pressure Sensor/Switch Circuit Range/Performance
The P0988 code indicates that the transmission control module (TCM) has detected a signal from the transmission fluid pressure (TFP) sensor or switch that is outside the expected range or not performing correctly. This sensor monitors hydraulic pressure within the transmission to ensure proper shift timing and line pressure. A range/performance issue means the sensor reading is either too high, too low, or erratic compared to the commanded pressure, often due to electrical faults, mechanical blockages, or internal transmission problems.
01. Most Common Causes
- Faulty transmission fluid pressure sensor
- Wiring or connector issues (open, short, corrosion)
- Low or contaminated transmission fluid
- Internal transmission mechanical failure (e.g., stuck valve, clogged passage)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Harsh or erratic shifting
- Transmission slipping or delayed engagement
- Reduced fuel economy
03. Step-by-Step Diagnosis
Step 1: Scan for additional codes and check freeze frame data.
Step 2: Inspect transmission fluid level and condition; top off or replace if necessary.
Step 3: Visually check wiring and connectors to the TFP sensor for damage or corrosion.
Step 4: Test the TFP sensor resistance and voltage output per manufacturer specifications.
Step 5: If sensor and wiring are OK, perform a transmission pressure test to identify internal issues.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances with this code, as it can cause harsh shifting, slipping, or further transmission damage. Have it diagnosed promptly.
How much does it cost to fix?▼
Repair costs vary; sensor replacement typically ranges from $150 to $400 including parts and labor. Internal transmission repairs can be significantly higher.