I have a 2001 L300 and my check engine light is on. The code is P1817 transmission position sensor. Where is this sensor located? I can't find anything on it ,

 

My best guess is its what we would call the neutral safety switch.
Although it does much more than that.
It is located on top of the transmission, the shift cable goes to it.
It is visible from under the hood,It may only need adjustment, many have slotted mounting
hole for adjustment.

 

I’ll see if that’s it. Thanks.

 

My non guess is that the code definition is

DTC P1817 TFP Valve Position Sw. - Reverse With Drive Ratio

More later

 

That’s correct, but I can’t find any info on that part or how to fix it.

 

P1817: Transmission Fluid Pressure Manual Valve Position Switch Reverse with Drive ratio OBD-II Trouble Code

The transmission fluid pressure manual valve position switch/TFP manual valve position switch uses fluid pressure from the manual valve to tell what gear has been selected. If the ECU sees that a drive ratio is been selected, but the TFP manual valve position switch thinks that reverse and has been selected, a P1817 diagnostic trouble code will be stored.

How Serious is the Code?

In order to compensate for the error, the ECU/TCM will command maximum line pressure inside the transmission. This can cause severe damage to the internal components.

Symptoms

Symptoms of a P1817 DTC include:

• Unusually harsh shifts
• Check engine light
• Limp Mode

Causes

• 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

What Repairs Will Fix P1817?

Repair any electrical shorts in the transmission fluid pressure manual valve position sensor circuit

Replace the TFP sensor

https://www.transmissionrepaircostguide.com/p1817/

 

The fsm says to inspect the wiring at the transmission control module, the transaxle connector and the transmission fluid pressure valve position sensor connector. Look for bent terminals, backed out terminals, damaged terminals, chafed wires, broken wire inside the insulation, moisture or corrosion.
Is this a hard code? This means can you clear it or does it not clear. If you can clear it how long until it comes back?