| Table 1: | Transmission Internal Mode Switch Logic |
| Table 2: | DTC P1825 Transmission IMS -- Illegal Range |
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 from the IMS 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 level at the PCM is high (B+) when the IMS is open and low when the switch is closed to ground. The state of each input is available for display on the scan tool. The four input parameters displayed are Input A , Input B, Input C and Input P (Parity).
If the PCM detects an invalid transmission range for 5 seconds with the engine running, then DTC P1825 sets. DTC P1825 is a Type D DTC.
Conditions for Running the DTC
| • | The system voltage is 9-18 volts. |
| • | The engine speed is at least 500 RPM for 5 seconds and not in fuel shutoff. |
Conditions for Setting the DTC
The PCM detects an invalid combination of IMS signals for 5 seconds.
Action Taken When the DTC Sets
| • | The PCM does not illuminate the malfunction indicator lamp (MIL). |
| • | The PCM stores DTC P1825 in PCM history. |
Conditions for Clearing the DTC
| • | A scan tool clears the DTC from the PCM history. |
| • | The PCM clears the DTC from the PCM history if the vehicle completes 40 consecutive warm-up cycles without an emission related diagnostic fault occurring. |
| • | The PCM cancels the DTC default actions when the fault no longer exists and the ignition switch is OFF long enough in order to power down the PCM. |
Diagnostic Aids
| • | Inspect the wiring for faulty electrical connections at the PCM, the transmission 20-way connector, the IMS connector and all other circuit connecting points for the following conditions: |
| - | A backed out terminal |
| - | A damaged terminal |
| - | Reduced terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| - | Moisture intrusion |
| - | Corrosion |
| • | When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. |
Gear Selector Position | Scan Tool IMS Range | |||
|---|---|---|---|---|
A | B | C | P | |
Park | On | Off | Off | On |
Park/Reverse | On | On | Off | On |
Reverse | On | On | Off | Off |
Reverse/Neutral | Off | On | Off | Off |
Neutral | Off | On | Off | On |
Neutral/Drive 4 | Off | On | On | On |
Drive 4 | Off | On | On | Off |
Drive 4/Drive 3 | On | On | On | Off |
Drive 3 | On | On | On | On |
Drive 3/Drive 2 | On | Off | On | On |
Drive 2 | On | Off | On | Off |
Drive 2/Drive 1 | Off | Off | On | Off |
Drive 1 | Off | Off | On | On |
Invalid Ranges | Off | Off | Off | Off |
On | Off | Off | Off | |
Off | Off | Off | On | |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests for a loose connection or connector related condition.
-
This step tests the PCMs ability to detect a state change on each input circuit.
-
This step tests the input circuits to the PCM on the engine side of the wiring harness.
-
This step tests the input circuits on the transmission side of the wiring harness.
-
Because of harsh conditions inside the transmission, repairing the automatic transmission (A/T) wiring harness assembly is not acceptable. It must be replaced if it is damaged in any way.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls | |
2 |
Important: Before clearing the DTCs, use the scan tool in order to record the Failure Records for reference. Using the Clear Info function will erase the stored Failure Records from the PCM. Refer to the Transmission Internal Mode Switch Logic table. Does the IMS A/B/C/P input match the Transmission Mode Switch Logic for each range? | -- | Go to Diagnostic Aids | |
Was a condition found? | -- | |||
Refer to Automatic Transmission Inline Harness Connector End View . Does the state of each of the IMS A/B/C/P inputs change to ON when it is grounded? | -- | |||
Inspect circuits 771 (BLK/WHT), 772 (YEL), 773 (GRY) and 776 (WHT) of the engine wiring harness for an open. Was a condition found? | -- | |||
6 | Inspect circuit 51 (BLK/WHT) of the engine wiring harness for an open. Refer to General Electrical Diagnosis in Wiring Systems. Was a condition found? | -- | ||
Inspect circuits 771 (PNK), 772 (DK BLU), 773 (ORN), 776 (PPL) and 1050 (BLK) of the automatic transmission wiring harness assembly for an open. Was a condition found? | -- | |||
8 | Repair the connector as necessary. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
9 | Repair the circuit(s) as necessary. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | -- | |
Replace the automatic transmission wiring harness assembly. Refer to Solenoids and Wiring Harness Replacement. Is the replacement complete? | -- | -- | ||
11 | Replace the transmission internal mode switch. Refer to Internal Mode Switch Replacement. Is the replacement complete? | -- | -- | |
12 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming in Engine Controls. Is the replacement complete? | -- | -- | |
13 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | System OK |
