Powertrain, generic (extended)

P2840 Shift Fork D Position Circuit

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

Likely causes

Electrical failure of the fork D position sensor
Damaged wiring between fork D sensor and the TCM
Transmission control module input or software fault

Symptoms

  • Gears of fork D withheld, gearbox skips them
  • Transmission warning lamp
  • Reduced driving comfort in emergency mode

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€200–2,500
Time1–6 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

shift fork dshift fork position sensor dwiring harness

Related codes

P2841P2842P2843P2844P283B

References: static.nhtsa.gov, gsi.ext.gm.com, fordservicecontent.com.