Circuit Description
The transmission internal mode switch (IMS) is a sliding contact switch attached to the selector detent inside the transmission side cover. The four inputs to the PCM indicate the position of the transmission range selector. The input voltage level at the PCM is high, B+, when the IMS is open and low when the switch is closed to ground. The four input parameters represented are Signals A, B, C and P, Parity. Refer to Transmission Internal Mode Switch Logic .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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HI values for all signals in all ranges indicates the ground circuit is OPEN.
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With the 20-way connector disconnected, all signals should indicate HI.
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If one circuit affects the other, this indicates a short between the two circuits.
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This step tests the internal transmission harness. If no fault is found in the harness, the fault will be in the switch.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 |
Does each range selected match the scan tool IMS display? | -- | Go to Intermittent Conditions in Engine Controls - 3.8L | Go to Step 2 |
Does the IMS A/B/C/P display the specified values for each range? | HI/HI/HI/HI | Go to Step 12 | Go to Step 3 | |
Do the scan tool IMS A/B/C/P signals all indicate HI? | -- | Go to Step 4 | Go to Step 8 | |
4 |
Refer to Automatic Transmission Inline 20-Way Connector End View . Does the voltage measure ignition voltage at all four terminals? | -- | Go to Step 5 | Go to Step 9 |
Connect a fused jumper wire from terminal F of the J 44152 signal A circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When signal A circuit (CKT 771) is grounded, do any other signal circuits indicate LOW? | -- | Go to Step 10 | Go to Step 6 | |
6 | Connect a fused jumper wire from terminal G of the J 44152 signal B circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When signal B circuit (CKT 772) is grounded, do any other signal circuits indicate LOW? | -- | Go to Step 10 | Go to Step 7 |
7 | Connect a fused jumper wire from terminal H of the J 44152 signal C circuit to ground while monitoring the scan tool IMS A/B/C/P parameter. Refer to Automatic Transmission Inline 20-Way Connector End View . When signal C circuit (CKT 773) is grounded, do any other signal circuits indicate LOW? | -- | Go to Step 10 | Go to Step 11 |
8 | Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate HI for a short to ground between the PCM connector C1 or C2 and the AT Inline 20-way connector. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 |
9 | Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS that did not indicate ignition voltage for an open between the PCM connector C1 or C2 and the AT Inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 |
10 | Test the affected signal circuits of the IMS for a shorted together condition between the PCM connector C1 or C2 and the AT Inline 20-way connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 16 |
Test the signal circuits (CKTs 771, 772, 773 and 776) of the IMS for an open or shorted condition between the AT Inline 20-way connector and the IMS. Refer to Circuit Testing in Wiring Systems. Did you find the condition? | -- | Go to Step 14 | Go to Step 15 | |
12 | Test the ground circuit (CKT 451) of the IMS for an open between the AT Inline 20-way connector and the ground connection to the chassis. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 17 | Go to Step 13 |
13 | Test the ground circuit (CKT 1050) of the IMS for an open between the AT Inline 20-way connector and the IMS. Refer to Testing for Continuity in Wiring Systems. Did you find the condition? | -- | Go to Step 14 | Go to Step 15 |
14 | Replace the automatic transmission wiring harness assembly. Refer to Wiring Harness Replacement . Did you complete the replacement? | -- | Go to Step 17 | -- |
15 | Replace the lever assembly-manual shaft detent with internal mode switch. Refer to Manual Shift Detent Lever with Shaft Position Switch Assembly Removal in Transmission Unit Repair Manual. Did you complete the replacement? | -- | Go to Step 17 | -- |
16 | Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 3.8L. Did you complete the replacement? | -- | Go to Step 17 | -- |
17 |
Does each selected transmission range match the scan tool IMS display? | -- | System OK | Go to Step 1 |
