4L80-E / 4L85-E Automatic Transmission

DTC P1810 (Diesel)















Circuit Description with 4L80-E / 4L85-E Automatic Transmission
The automatic Transmission Fluid Pressure (TFP) manual valve position switch consists of five normally-open pressure switches. The Powertrain Control Module (PCM) supplies battery voltage to each range signal. By grounding one or more of these circuits through various combinations of the pressure switches, the PCM 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 chart stored in memory.
The TFP manual valve position switch 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,D2is indicated. When the transmission 20-way connector is disconnected, the ground potential for the three range signals to the PCM is removed, and with the ignition ON, D2 is indicated.
If the PCM 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 B DTC.

Conditions for Running the DTC
^ The system voltage is 8-18 volts.
^ The APP angle is greater than 12 percent.
^ The engine speed is greater than 475 RPM for greater than 7 seconds.
^ No AT OSS DTCs P0502 or P0503.
^ No ATISS 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.
^ The engine speed is less than 3750.
^ Not in fuel cut-off.
^ The engine torque is 108 - 644 Nm (80 - 475 ft. lbs.).
^ The engine vacuum is 0 - 15 psi (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 PCM detects an illegal TFP manual valve position switch state for 25.5 seconds.

Condition 2
^ The engine speed is less than 50 RPM for 1.5 second; then 50-575 RPM for 0.3 second; then the engine speed is greater than 575 RPM.
^ The vehicle speed is less than 4 km/h (2.5 mph).
^ The PCM detects the gear range as D2 before and after start-up.
^ All conditions are met for 7.5 seconds.

Condition 3
^ The vehicle speed is greater than 8 km/h (5 mph).
^ The TP angle is greater than 12 percent.
^ The PCM detects the following when the TFP switch indicates:
- P/N when the ratio indicates third or fourth for greater than 15 seconds.
- REVERSE when the ratio indicates D4, D3, D2 and D1 for greater than 15 seconds.
- D4, D3, D2 and D1 when the ratio indicates REVERSE for greater than 5 seconds.

Action Taken When the DTC Sets
^ The PCM illuminates the Malfunction Indicator Lamp (MIL) during the second consecutive trip in, which the Conditions for Setting the DTC are met.
^ The PCM commands maximum line pressure.
^ The PCM assumes D4 for the PRNDL shift pattern.
^ The PCM freezes shift adapts.
^ The PCM records the operating conditions when the Conditions for Setting the DTC are met. The PCM stores this information as Freeze Frame and Failure Records.
^ The PCM stores the DTC P1810 in PCM history during the second consecutive trip in, which the Conditions for Setting the DTC are met.

Conditions for Clearing the MIL/DTC
^ For Federal and California emissions, the PCM turns OFF the MIL during the third consecutive trip in, which the diagnostic test runs and passes.
^ A scan tool can clear the MIL/DTC.
^ For Federal and California emissions, the PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring.
^ For vehicles equal to or greater than 15,000 lbs GVW, the PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring.
^ The PCM 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 PCM.

Diagnostic Aids
^ Refer to Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic (Gas) or Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic (Diesel) for the normal range signals and the illegal combinations.
^ 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 PCM to power down, and then restart the vehicle.
^ DTC P1810 can be set falsely by low pump pressure, a stuck pressure regulator, or unit fill from overhaul and pan removal.
^ DTC P1810 can be set by a slipping forward clutch. It may allow the PCM to see a 2.08:1 ratio (REVERSE) when the manual valve position is indicated as D4.
^ DTC P1810 may be inhibited from passing if the state of the battery is low, or there is a low cranking voltage. To pass DTC P1815, turn the ignition switch to the ON position with the engine OFF. Check that all the range signal switches (A, B. C) read OFF, OFF, OFF. Start the vehicle, and move the PRNDL through each selected transmission range.
^ DTC P1810 defaults to an elevated line pressure condition which may result in TCC partial apply. This may induce idle surge and engine stall.

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 PCM to the transmission 20-way connector.