P1818

Steps 1-6:

Steps 7-15:

Steps 16-20:

DTC P1818
Circuit Description
The transmission manual shift shaft switch assembly is a sliding contact switch attached to the control valve body within the transmission. The four inputs to the Transmission Control Module (TCM) from the switch indicate which position is selected by the transmission selector lever. This information is used for engine controls as well as determining the transmission shift patterns. The input voltage at the TCM is high when the switch is open and low when the switch is closed to ground. The state of each input is displayed on the scan tool as IMS. The four IMS input parameters represented are Signal A, Signal B. Signal C and Signal P (Parity).
If the TCM detects that the gear selector lever is in D2, D3, D4, or D5 while the gear ratio indicates that the vehicle is in Reverse, then DTC P1818 sets. DTC P1818is a type B DTC.

Conditions for Running the DTC
^ The system voltage is 8 - 18 volts.
^ The engine run time is greater than 5 seconds.
^ No throttle system DTC'S P1791 or P1795.
^ No OSS DTC'S P0722 or P0723.
^ No ISS DTC'S P0716 or P0717.
^ No IMS DTC'S P1815, P1818, P1820, P1822, P1823, P1825 or P1826.
^ No shift solenoid performance DTC'S P0751, P0752, P0756, P0757, P0761, or P0762.
^ No engine torque signal DTC P1779.
^ The Accelerator Pedal Position (APP) angle is greater than 5 percent.
^ The vehicle speed is greater than 8 km/h (5 mph).
^ The engine torque is 20 - 350 Nm (15 - 258 ft. lbs.).
^ The gear ratio is 2.95:1 to 3.10:1.

Conditions for Setting the DTC
The IMS indicates that the gear selector is in a forward range while the gear ratio is 2.95 - 3.10 for 3 seconds or greater.

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 assumes a D5 shift pattern.
^ The TCM discontinues updating Transmission Adaptive Pressure (TAP) memory cells.
^ 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 P1818 in TCM history.

Conditions for Clearing the DTC
^ The ECM turns OFF the MIL after the sixth 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.

Test Description
The numbers below refer to the step numbers on the diagnostic table.
3. All HI values, in both Park and Drive 5, indicate the ground circuit is OPEN.
5. With the transmission 20-way connector disconnected, all TR signals should indicate HI.
7. If one circuit affects the other, this indicates a short between the two circuits.
13. This step tests the internal transmission harness. If no fault is found in the harness, the fault will be in the switch.