4L80-E / 4L85-E Automatic Transmission

Circuit Description
The automatic transmission fluid pressure (TFP) manual valve position switch consists of five normally-open pressure switches. The vehicle control module (VCM) supplies battery voltage to each range signal. By grounding one or more of these circuits through various combinations of the pressure switches, the VCM detects what manual valve position has been selected, and compares the actual voltage combination of the switches to a TFP manual valve position switch combination table stored in memory.

The TFP manual valve position switch assembly cannot distinguish between PARK and NEUTRAL because the monitored valve body pressures are identical in both cases. With the ignition ON and the engine OFF, D2 is indicated. When the transmission 20-way connector is disconnected, the ground potential for the three range signals to the VCM is removed, and with the ignition ON, D2 is indicated.

If the VCM detects an invalid state of the TFP manual valve position switch circuit by deciphering the TFP manual valve position switch inputs, then DTC P1810 sets. DTC P1810 is a type D DTC. For California emissions vehicles DTC P1810 is a type B DTC.

Conditions for Running the DTC
^ The system voltage is 10-16.0 volts.
^ The engine speed is greater than 500 RPM for 7 seconds.
^ No OSS DTCs P0502 or P0503.
^ No ISS DTCs P0716 or P0717.
^ No PSA DTC P1810.
^ No MAP DTCs P0106, P0107 or P0108.
^ No 1-2 SS DTCs P0751 or P0753.
^ No 2-3 SS DTCs P0756 or P0758.
^ Not in fuel cut off.
^ The engine torque is:
- 108-540 N.m (80-400 lb ft)
- 108-675 N.m (80-500 lb ft)
^ The engine vacuum is 0-105 kPa.

Conditions for Setting the DTC
DTC P1810 sets during the second consecutive trip in which any of the following condition occurs:

Condition 1
The VCM detects an illegal TFP manual valve position switch state for 60 seconds.

Condition 2
^ The engine speed is less than 50 RPM for 0.3 second; then between 50 and 550 RPM for 0.3 second; then the engine speed is greater than 550 RPM.
^ The vehicle speed is less than 4 km/h (2.5 mph).
^ The VCM detects the gear range as D2 before and after start up.
^ All conditions are met for 7 seconds.

Condition 3
^ The vehicle speed is greater than 8 km/h (5 mph).
^ The TP angle is greater than 10%. The TFP switch indicates the following:
- P/N when the ratio indicates less than 1.05:1 for greater than 15 seconds.
- Reverse when the ratio indicates D4, D3, D2, and D1for greater than 5 seconds.
- D4, D3, D2, and D1 when the ratio indicates reverse for greater than 7 seconds.

Action Taken When the DTC Sets
^ The VCM illuminates the Malfunction Indicator Lamp for California emission vehicles.
^ The VCM commands maximum line pressure.
^ The VCM assumes D4 for the PRNDL shift pattern.
^ The VCM freezes shift adapts.
^ The VCM commands the TCC on in commanded fourth gear.
^ The VCM stores DTC P1810 in VCM history.

Conditions for Clearing the MIL/DTC
^ For California emissions, the VCM turns OFF the MIL during the third consecutive trip in which the diagnostic test runs and passes.
^ A scan tool clears the DTC from VCM history.
^ For California emissions, the VCM clears the DTC from VCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring.
^ For Federal emissions, the VCM clears the DTC from VCM history if the vehicle completes 40 consecutive warm-up cycles without a non-emission related diagnostic fault occurring.
^ The VCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the VCM.

Diagnostic Aids
^ Refer to Range Signal for the normal range signals and the illegal combinations.
^ Inspect the wiring at the VCM, the transmission connector and all other circuit connecting points for the following conditions:
- A backed out terminal
- A damaged terminal
- Reduced terminal tension
- A chafed wire
- A broken wire inside the insulation
- Moisture intrusion
- Corrosion
^ When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change.
^ DTC P1810 can be falsely set during a fluid fill procedure. After refilling the fluid, cycle key down then start and run the vehicle for 20 seconds. key down and allow the VCM to power down, and then restart the vehicle.
^ DTC P1810 can be set falsely by low pump pressure or a stuck pressure regulator.
^ DTC P1810 can be set by a rolled forward clutch piston seal. It may allow the VCM to see a 2.08:1 ratio (reverse) when the manual valve position is indicated as D4.
^ First diagnose and clear any engine DTCs or TP sensor codes that are present. Then inspect for any transmission DTCs that may have reset.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step tests the indicated range signal to the manual valve that is actually selected.
4. This step tests the voltage from the VCM to the transmission 20-way connector.