P1816
DTC P1816
Circuit Description
The automatic transmission fluid pressure (TFP) manual valve position switch consists of 5 pressure switches, 2 normally-closed and 3 normally-open, and a transmission fluid temperature (TFT) sensor combined into 1 unit. The combined unit mounts on the valve body. The transmission control module (TCM) supplies ignition voltage for each range signal. By grounding 1 or more of these circuits through various combinations of the pressure switches, the TCM detects which manual valve position you select. The TCM 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. With the engine OFF and the ignition switch in the ON position, the TFP manual valve position switch indicates PARK/NEUTRAL. Disconnecting the AT inline 20-way connector removes the ground potential for the 3 range signals to the TCM. In this case, with the engine OFF, and the ignition switch in the ON position, D2 will be indicated.
When the TCM detects an invalid state of the TFP manual valve position switch circuit by deciphering the TFP manual valve position switch inputs, then DTC P1816 sets. DTC P1816 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1816 Transmission Fluid Pressure (TFP) Valve Position Switch Indicates Park/Neutral (P/N) with Drive Ratio
Conditions for Running the DTC
^ No VSS DTCs P0722, or P0723.
^ The system voltage is 8 - 18 volts.
^ The engine speed is less than 50 RPM, then between 50 - 650 RPM for 0.75 seconds, then greater than 650 RPM for 5 seconds.
^ OSS speed less than 250 RPM.
Conditions for Setting the DTC
DTC P1816 sets when the TCM detects one of the following conditions for 13 seconds.
^ PARK/NEUTRAL indicated with a 1st gear ratio.
^ PARK/NEUTRAL indicated with a 2nd gear ratio.
^ PARK/NEUTRAL indicated with a 3rd gear ratio.
^ PARK/NEUTRAL indicated with a 4th gear ratio.
Action Taken When the DTC Sets
^ The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the Conditions for Setting the DTC are met.
^ The TCM commands maximum line pressure.
^ The TCM freezes transmission adaptive functions.
^ The TCM inhibits TCC engagement.
^ The TCM commands 4th gear.
^ At the time of the first failure, the TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as a Failure Record.
^ At the time of the second failure, the ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as a Freeze Frame.
^ The TCM stores DTC P1816 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met.
Conditions for Clearing the DTC
^ The ECM turns OFF the MIL after the 4th consecutive drive trip in which the TCM does not send a MIL illumination request.
^ A scan tool can clear the DTC.
^ The TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without a non-emission related diagnostic fault occurring.
^ The TCM cancels the DTC default actions when the ignition is OFF long enough in order to power down the TCM.
Diagnostic Aids
^ Refer to the Transmission Fluid Pressure (TFP) Manual Valve Position Switch Logic for the normal range signals and the invalid combinations. On the table, LOW is 0 volts, HI is ignition voltage.
^ Sediment in the valve body may cause improper operation of the TFP manual valve position switch. If sediment intrusion is suspected, clean the valve body and replace the TFP manual valve position switch.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. This step compares the indicated range signal to the selected manual valve position.
5. This step tests for correct voltage from the TCM to the AT inline 20-way connector.
