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 transmission control module (TCM) provides battery voltage on the two range signal circuits. By grounding one or more of the switches with fluid pressure from the manual shift valve, the TCM detects the selected gear range. When you disconnect the transmission electrical connector and the ignition is ON, the ground potential for the range signals from the TCM will be removed, and an invalid gear range will be indicated. Refer to Transmission Fluid Pressure Manual Valve Position Switch Logic .
When the TCM 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 P0107 or P0108. |
| • | No TP DTCs P0120 or P0220. |
| • | No ISS DTCs P0716 or P0717. |
| • | No OSS DTCs P0722 or P0723. |
| • | No SS valve performance DTCs P0751, P0752, P0756, or P0757. |
| • | No SS valve electrical DTCs P0973, P0974, P0976, or P0977. |
| • | The engine is running for 5 seconds. |
| • | The Calc. Throttle Position is 3 percent or more. |
| • | The engine torque is greater than 20 N·m (15 lb ft). |
| • | The output speed is 153 RPM or more. |
| • | The transmission fluid temperature is greater than 0°C (32°F). |
Conditions for Setting the DTC
The TCM detects a PARK, NEUTRAL, or a drive range with a REVERSE ratio for 3 seconds.
Action Taken When the DTC Sets
| • | The TCM illuminates 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 records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Freeze Frame and Failure Records. |
| • | The TCM stores DTC P1818 in TCM history during the second consecutive trip in which the Conditions for Setting the DTC are met. |
Conditions for Clearing the MIL/DTC
| • | The TCM 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 TCM clears the DTC from TCM history if the vehicle completes 40 warm-up cycles without an emission related diagnostic fault occurring. |
| • | The TCM cancels the DTC default actions when the ignition switch 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.
-
This step tests the indicated range signal to the manual valve range actually selected.
-
This step tests for correct voltage from the TCM.
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 TCM. 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 Sw. Sig. B / Sig. C parameter indicate HI for all range states? | Go to Step 6 | Go to Step 9 |
Refer to Automatic Transmission Inline 20-Way Connector End View . 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 Sw. 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 Sw. 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 TCM connector 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 TCM connector 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 TCM connector 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 TCM. 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 |
