Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
DTC 28, Transmission Range Pressure Switch Circuit Fault: Notes
Transmission range pressure switch assembly consists of 5 pressure switches (2 normally closed, 3 normally open), and a fluid temperature sensor combined into one unit and mounted on valve body. PCM supplies voltage to each range signal. By grounding one or more of these circuits through various combinations of pressure switches, PCM detects which manual valve position has been selected. With ignition on and engine off, Park/Neutral will be indicated. When transmission electrical connector is disconnected, ground potential for the 3 signals to PCM will be removed, and with ignition on, D2 will be indicated. DTC 28 will set when range signals "A" and "C" are both zero volts (on) for 2 seconds.
PCM will default to harsh shifts, D4 shift control. TCC will be inhibited, and if in hot mode, 4th gear will not be available. DTC 28 will be stored in PCM memory, but will not turn on MIL.
- This test checks indicated range signal to manual valve position actually selected.
- This test checks for correct voltage from PCM to transmission external connector.
- This test checks for short to ground from PCM to transmission external connector in any one of the 3 circuits.
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.