P0991
Transmission Fluid Pressure Sensor/Switch E Circuit Intermittent
Transmission
Generic OBD-II
Medium
What it means
P0991 means the signal from transmission fluid pressure sensor/switch "E" is cutting out intermittently. The control module uses this reading to manage line pressure and shifting, so a dropping signal can cause occasional harsh or unpredictable shifts. Because the fault is intermittent, symptoms come and go, and a loose connector or chafed wire is a common cause.
Medium
Can I keep driving? Usually drivable — the fault is intermittent — but occasional harsh or unpredictable shifts can occur; have it inspected.
Common symptoms
What you'll notice
- Intermittent check-engine light
- Occasional harsh or delayed shifts
- Erratic or unpredictable gear changes at times
- Momentary loss of smooth power delivery from the transmission
Common causes
Most likely first
- Intermittent wiring or connector fault in the sensor circuitLikely
- Loose or corroded terminals at the pressure sensor/switch ECommon
- Faulty transmission fluid pressure sensor/switch ECommon
- Vibration or chafing intermittently breaking the circuitLess often
- Intermittent fault inside the transmission control module (TCM)Less often
How to diagnose & fix
Work through it in order
- Read freeze-frame data to see the conditions when the code sets.
- Wiggle-test the sensor harness and connector while watching live data for dropouts.
- Clean and reseat connectors; repair any chafed or corroded wiring.
- Test the pressure sensor/switch E signal and replace it if it drops out.
- If the circuit is solid, have the TCM checked for an internal fault. Clear and road-test.
FAQ
Quick answers
Is it safe to drive with P0991?+
Yes, generally — the fault comes and goes — but occasional erratic shifts mean you should fix it before it becomes constant.
Can I just clear P0991?+
Intermittent codes often stay away for a while after clearing, which makes them hard to confirm; fix the loose connection or sensor for a lasting result.
Related codes
Often seen with P0991
Read & clear P0991 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX