Circuit Description
The automatic transmission fluid pressure (TFP) manual valve position switch consists of three pressure switches. Two of the switches are normally-open, and determine gear range selection. The third switch is normally-closed, and detects torque converter clutch (TCC) release fluid pressure. The TFP manual valve position switch also contains the automatic transmission fluid temperature (TFT) sensor. These components are combined into one unit, attached to the control valve body.
The powertrain control module (PCM) provides battery voltage on the three signal circuits. By grounding one or more of the switches with fluid pressure from the manual shift valve, the PCM detects the selected gear range. When you disconnect the transmission electrical connector and the ignition is ON, the ground potential for the two range signals from the PCM will be removed, and an invalid gear range will be indicated. Refer to Transmission Fluid Pressure Manual Valve Position Switch Logic .
When the PCM detects Park, Neutral, or a drive gear with a REVERSE ratio, DTC P1818 sets. DTC P1818 is a type B DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1818 Transmission Fluid Pressure (TFP) Valve Position Switch Indicates Drive without Drive Ratio
Conditions for Running the DTC
| • | No MAP DTCs P0106, P0107, or P0108. |
| • | No TP DTCs P0122 or P0123. |
| • | No OSS DTCs P0502 or P0503. |
| • | No ISS DTCs P0716 or P0717. |
| • | No shift solenoid performance DTCs P0751, P0752, P0756, or P0757. |
| • | No shift solenoid electrical DTCs P0753 or P0758. |
| • | The engine is running for greater than 5 seconds and not in fuel cut off. |
| • | The vehicle speed is 5 km/h (3 mph) or greater. |
| • | The TPS is greater than 10 percent. |
| • | The engine torque is greater than 34 N·m (25 lb ft). |
Conditions for Setting the DTC
The PCM detects Park, Neutral or a drive range with a REVERSE ratio for 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 assumes a D4 shift pattern. |
| • | The PCM commands an alternate coast shift pattern where downshifts occur at higher speeds while coasting. |
| • | The PCM freezes transmission adaptive functions. |
| • | 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 DTC P1818 in PCM history during the second consecutive trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the MIL/DTC
| • | 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. |
| • | The PCM clears the DTC from PCM history if the vehicle completes 40 warm-up cycles without an emission-related diagnostic fault occurring. |
| • | The PCM cancels the DTC default actions when the ignition switch is OFF long enough in order to power down the PCM. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests the indicated range signal to the manual valve range actually selected.
-
This step tests for correct voltage from the PCM.
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
2 | Did you perform the Transmission Fluid Checking Procedure? | Go to Step 3 | Go to Transmission Fluid Check |
Important: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and Failure Records from the PCM. Does each selected transmission range match the scan tool TFP switch display? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 4 | |
4 |
Did the linkage require adjustment? | Go to Step 16 | Go to Step 5 |
5 |
Does the scan tool TFP Switch Sig. B/Sig. C parameter indicate HI for all range states? | Go to Step 6 | Go to Step 9 |
Does the voltage measure ignition voltage at both terminals? | Go to Step 7 | Go to Step 10 | |
7 | Connect a fused jumper wire from the TFP signal B circuit of the J 44152 to ground while monitoring the scan tool TFP Switch Sig. B/Sig. C parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When the TFP signal B circuit is grounded, do any other signal circuits indicate LOW? | Go to Step 11 | Go to Step 8 |
8 | Connect a fused jumper wire from the TFP signal C circuit of the J 44152 to ground while monitoring the scan tool TFP Switch Sig. B/Sig. C parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When the TFP signal C circuit is grounded, do any other signal circuits indicate LOW? | Go to Step 11 | Go to Step 12 |
9 | Test the signal circuits of the TFP manual valve position switch that did not indicate HI for a short to a ground between the PCM connector C2 and the AT inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs . Did you find and correct a condition? | Go to Step 16 | Go to Step 15 |
10 | Test the signal circuits of the TFP manual valve position switch that did not indicate ignition voltage for an open between the PCM connector C2 and the AT inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs . Did you find and correct a condition? | Go to Step 16 | Go to Step 15 |
11 | Test the affected signal circuits of the TFP manual valve position switch for a shorted together condition between the PCM connector C2 and the AT inline 20-way connector. Refer to Circuit Testing and Wiring Repairs . Did you find and correct a condition? | Go to Step 16 | Go to Step 15 |
12 | Test the affected signal circuits of the TFP manual valve position switch for an open or shorted condition between the AT inline 20-way connector and the TFP manual valve position switch. Refer to Circuit Testing . Did you find the condition? | Go to Step 13 | Go to Step 14 |
13 | Replace the automatic transmission wiring harness. Refer to Wiring Harness Replacement . Did you complete the replacement? | Go to Step 16 | -- |
14 | Replace the TFP manual valve position switch. Refer to Transmission Fluid Pressure Manual Valve Position Switch Replacement . Did you complete the replacement? | Go to Step 16 | -- |
15 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Is the replacement complete? | Go to Step 16 | -- |
16 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | Go to Step 17 | Go to Step 2 |
17 | With the scan tool, observe the stored information, capture info and DTC info. Does the scan tool display any DTCs that you have not diagnosed? | System OK |
