With VCM-A

Transmission Range (TR) Pressure Switch Assembly Circuit Check Diagnostic Chart:

Transmission Range (TR) Pressure Switch Assembly Wiring Assembly:

CIRCUIT DESCRIPTION
The Transmission Range (TR) switch assembly consists of five pressure switches (two normally closed and three normally open), and a Transmission Fluid Temperature (TFT) sensor combined into one unit and mounted on the valve body. The Vehicle Control Module (VCM-A) supplies battery voltage to each range signal. By grounding one or more of these circuits through various combinations of the pressure switches, the VCM-A detects what manual valve position has been selected and compares the actual voltage combination of the switches to a (TR) combination chart stored in memory.
The (TR) assembly cannot distinguish between Park and Neutral because the monitored valve body pressures are identical in both cases. With ignition "ON" and engine "OFF" P/N will be indicated. When transmission electrical connector is disconnected, the ground potential for the three range signals to the VCM-A will be removed, and with ignition "ON," D2 will be indicated.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test checks the indicated range signal to the manual valve position actually selected.
2. This test checks for correct voltage from the VCM-A to the transmission external connector.
3. This test checks for a short to ground or open circuit from the VCM-A to the transmission external connector in any one of the three circuits.

Range Signal Expected Readings:

DIAGNOSTIC AIDS
Refer to accompanying chart for various A/B/C range combinations. Check all wiring connectors for proper terminal tension. For current DTC P1810, range signal will default to "D4" while A/B/C range values continue to read actual "TR Pressure Switch" output for each range selection.
Refer to "TR Pressure Switch Assembly Resistance Check" or "Functional Test Procedure".
If circuit 1225 is grounded or open, 4th gear is inhibited, no code will set and no MIL illumination.