The P1811 diagnostic trouble code usually appears when the transmission control module detects an unusually long shift time. On average, most acceptable shift time parameters are set at 0.6 seconds. Anything longer will cause the TCM to raise the line pressure, which will cause usually harsh shifts.
How Serious is the Code?
A P1811 diagnostic trouble code means the hydraulic line pressure has been raised to compensate for excessively worn clutches or other components. If left unchecked, this excessive line pressure can cause serious damage to other control components, making a small problem a lot worse.
Symptoms of a P1811 include:
- Longer than average shift times
- Unusually hard shifts
- Failing pressure control solenoid/EPC solenoid
- Worn clutches
- Worn accumulators
- Excessive valve body wear
- Malfunctioning MAF sensor causing lowered commanded line pressure
How to Diagnose the Code?
The first step to diagnosing a P1811 DTC is to examine the condition of the automatic transmission fluid. If metal fragments are present, the problem is most likely a failed hard part like it clutch pack or drum. If no issues are discovered with the ATF, then further investigation will be needed to determine if the problem lies with a failed pressure control solenoid.
Common Mistakes When Diagnosing
One of the most common mistakes made with diagnosing a P1811 diagnostic trouble code, is automatically assuming that the pressure control solenoid/EPC solenoid is to blame. If the vehicle has a lot of miles on it, it may be wise to investigate the transmission for signs of other issues that could cause this problem.
What Repairs Will Fix P1811?
Replace pressure control solenoid/EPC solenoid
Replace worn clutches
Replace worn accumulators
Repair valve body
Replace MAF sensor