P2840 code meaning
Shift Fork D Position Circuit
Powertrain system Generic code P28xx codes Check engine light
What P2840 means
P2840 is the overall circuit code for the shift fork D position input. Mercedes-Benz is the one maker that publicly documents it: in the 8G-DCT (transmission 724.1) of its compact models, P284000 marks an electrical fault of the fork D sensor, and the gearbox has a fifth fork E with its own codes from P2863 upward. The other two published dual-clutch strategies skip this code. GM's Corvette software treats fork D as rod 4 on the even shaft and reports its electrical faults as P2842, P2843 or P2844, and Ford's TR9070 summary does the same for rod position sensor 4. With the position of fork D unknown, the module cannot confirm whether its gear is in or out and normally withholds those ratios until the fault is gone.
P2840 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P2840
- Gears of fork D withheld, gearbox skips them
- Transmission warning lamp
- Reduced driving comfort in emergency mode
Common causes of P2840
- Most likelyElectrical failure of the fork D position sensor
- PossibleDamaged wiring between fork D sensor and the TCM
- Less likelyTransmission control module input or software fault
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Shift fork dShift fork position sensor dWiring harness
What each part of P2840 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 2 | Generic code (second SAE range): it means the same on every make. |
| 8 | Area: transmission. |
| 40 | The exact fault in that area. |
What to do next
- Note P2840 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P2840
What does P2840 mean?
P2840 means "Shift Fork D Position Circuit". P2840 is the overall circuit code for the shift fork D position input. It is a generic code, so it means the same on every make.
Is it safe to drive with P2840?
Drive gently and only to a workshop. With P2840 the car can go into limp mode (reduced power) to protect itself.
Will P2840 fail an emissions test?
Yes, it can. P2840 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P2840 to fix?
Difficulty: workshop only. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will P2840 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.