P2804: Transmission Range Sensor B Circuit Intermittent
What to do
Apply the parking brake every time you park, and treat the selector display with suspicion. The transmission has lost one of the two witnesses it uses to confirm which range it is in — check the car is truly holding before stepping away, and expect the occasional refused shift or reluctant start while it protects itself. Repair promptly; the second sensor is now the only one.
What this code means
Transmission range sensor B's signal is cutting in and out.
An intermittent signal is a connection fault until proven otherwise. A part that has failed reads failed all day; a signal that comes and goes with vibration and temperature is a connector or a chafed run of harness telling you where to look.
A second range sensor exists because the first one guarding park is not enough. The range sensor reports which gear range the transmission is actually in — the fact behind the selector display, the reverse lamps, and the rule that the starter only turns in park or neutral. Shift-by-wire designs duplicate it: with no mechanical cable to fall back on, the module wants two independent reports before it trusts either, especially about park.
Sensor B failing rarely strands the car; it removes the cross-check. The module can usually carry on watchfully using sensor A — but a car that misreports its range is a car that can roll away or start in gear, so expect caution: a flashing or wrong selector display, refusal to leave park, or a start that needs a second try.
These sensors fail the way all position sensors do — wear on the resistive track at the positions used most, water in a connector low on the gearbox, a harness chafed where it flexes. On cable-operated designs the sensor can also simply be out of adjustment, reading between ranges while the gearbox itself is exactly where it should be.
Likely causes
Start here
- Faulty transmission range sensor · specialist
- Misadjusted transmission range sensor · moderate
- Corroded transmission connector · specialist
Less common
- Damaged transmission wiring harness · specialist
Rare
- Faulty transmission control module · specialist
Symptoms
Components involved
Information, not instruction
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Community experience
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