Chassis, generic

C05D7 Brake Transmission Shift Interlock (BTSI) Control Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Covers the output that drives the brake transmission shift interlock, the solenoid that keeps the selector in park until the brake pedal is pressed. In the US, FMVSS 114 has required this lock since 1 September 2010 on vehicles up to 4,536 kg fitted with an automatic gearbox and a park position. A patent by Pontiac Coil shows the usual layout: a spring holds a blocking pin in the locked position, and a transistor energizes the coil only with ignition on and brake switch closed, so the system fails locked. The code points to the driver stage, wiring or coil. No manufacturer publishes C05D7; Ram logs P0928-00 for an internal BTSI fault in its rotary shifter. P081F is the signal correlation counterpart.

Likely causes

Interlock solenoid coil open or shorted
Damaged wiring or corroded connector at the shifter
Driver stage in the shifter or body module faulty
Brake light switch signal missing, so the lock is never released

Symptoms

  • Selector cannot be moved out of park despite pressing the brake
  • Selector leaves park without the brake applied
  • No clicking of the interlock when the brake is pressed

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–700
Time0.5–2.5 h

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

Parts involved

btsi solenoid

Related codes

P081FP0928P0929P0930P0931

References: law.cornell.edu, patents.google.com, static.nhtsa.gov.