What does it mean?
P1815 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: A/T Manual Shaft Shift Switch Circuit Malfunction (5L40-E) .
Symptoms
- Check engine lamp on and the gear position display shows dashes or the wrong letter
- Engine cranks in Neutral but not in Park, or will not crank at all
- Reverse lamps stay dark or come on in the wrong range
- Transmission starts off in a high gear and engages with a thump
- Harsh, delayed engagement and limp mode with reduced drivability
Likely causes
- Manual shaft or selector linkage out of adjustment, so the switch never lines up with a valid detent
- Worn or burnt contacts inside the switch producing a dead spot in one range
- Water, salt or transmission fluid in the switch connector corroding the pins
- Chafed harness on the transmission case shorting a range wire to ground or to another circuit
- Bent, loose or stretched shift cable letting the selector and the shaft disagree
- Failed switch assembly with an internally open track
- Loss of switch supply voltage from a blown fuse or a corroded splice
How to fix it
- Read the codes and compare the range reported on the scan tool with the selector position at each detent
- Check the shift cable and manual shaft adjustment first, and confirm the selector reaches each detent fully
- Inspect the switch connector for corrosion, moisture and fluid intrusion, and check the loom along the case for chafe
- Back-probe the range circuits and watch each one change state as the selector is moved through every position
- Verify the switch supply voltage and ground with the key on
- Adjust or realign the switch to specification before replacing it
- Renew the switch if a range stays dead after adjustment, then verify the range display through the full sweep