The ECUs uses a signal from the transmission fluid pressure manual valve position switch / TFP manual valve position switch to calculate line pressure based on the selected gear ratio. A P1818 DTC means the TFP manual valve switch thinks that Drive is selected, but the ECU sees a different gear.
How Serious is the Code?
When there is a discrepancy between the indicated gear ratios, the ECU/TCM will set the maximum line pressure to ensure that gear changes can happen. However, that can cause extensive damage to the internal components.
Symptoms of a P1818 DTC include:
- Hard gear changes
- Check engine light
- Limp Mode
- Failed transmission fluid pressure manual valve position switch/TFP switch
- Short in the TFP valve position switch wiring harness
- Poor connection in the TFP valve positions switch circuit
How to Diagnose the Code?
Determining the cause of a P1818 diagnostic trouble code will require electrical tests to be performed on the transmission fluid pressure manual valve position switch.
What Repairs Will Fix P1819?
Repair any electrical shorts in the transmission fluid pressure manual valve position sensor circuit
Replace the TFP sensor
P1810 – Transmission Fluid Pressure Manual Valve Position Switch
P1816 – Transmission Fluid Pressure Manual Valve Position Switch Park/Neutral with Drive ratio
P1818 – Transmission Fluid Pressure Manual Valve Position Switch Drive without Drive ratio