Circuit Description
The transmission control module (TCM) uses the ratio control motor to control the speed ratio. The ratio control motor is a linear position device, which changes the speed ratio by accurately controlling the position of the variable ratio control valve. Movement of the variable ratio control valve allows fluid to be applied and exhausted from the primary feed limit circuit. The TCM controls the ratio control motor by grounding four control circuits with power being supplied directly from the fuse block - underhood. The TCM monitors the status of the four low control circuits and can detect a short to power or a short to ground/open.
When either of these failures is detected, DTC P1885 sets. DTC P1885 is a type A DTC.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P1885 Ratio Control Motor Coil B1 Control Circuit
Conditions for Running the DTC
The engine speed is greater than 500 RPM for 5 seconds.
Conditions for Setting the DTC
The TCM detects an open, a short to ground, or a short to voltage on the ratio control motor B1 control circuit for 0.56 seconds.
Action Taken When the DTC Sets
| • | The TCM requests the ECM to illuminate the malfunction indicator lamp (MIL). |
| • | The TCM moves the speed ratio towards a target ratio and then freezes ratio changes. |
| • | The TCM discontinues use of the closed loop ratio control algorithm. This causes the speed ratio to be defaulted and possibly not accurate. The resulting open loop control may or may not provide optimum ratio performance. |
| • | The ECM records the operating conditions when the Conditions for Setting the DTC are met. The ECM stores this information as Freeze Frame and Failure Records. |
| • | The TCM records the operating conditions when the Conditions for Setting the DTC are met. The TCM stores this information as Failure Records. |
| • | The TCM stores DTC P1885 in TCM history. |
Conditions for Clearing the MIL/DTC
| • | The ECM turns OFF the MIL after the third consecutive drive trip in which the TCM does not send a MIL illumination request. |
| • | 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. |
Diagnostic Aids
| • | Inspect the connectors at the TCM, the transmission, and all other circuit connecting points for an intermittent condition. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
| • | Inspect the circuit wiring for an intermittent condition. Refer to Testing for Electrical Intermittents in Wiring Systems. |
Step | Action | Values | Yes | No | ||||
|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||
2 |
Important:
Is DTC P1883, P1884, or P1886 also set? | -- | Go to Step 3 | Go to Step 4 | ||||
3 | Test the ignition 1 voltage circuit for an open between the fuse block - underhood and the AT inline 20-way connector. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find the condition? | -- | Go to Step 19 | Go to Step 16 | ||||
4 | Using the scan tool, select Ratio Ctrl. Mtr. B1 Status. Does the scan tool display OPEN/SHORT TO GND? | -- | Go to Step 6 | Go to Step 5 | ||||
5 | Does the scan tool display SHORT TO VOLTS? | -- | Go to Step 7 | Go to Intermittent Conditions in Engine Controls - 2.2L (L61) | ||||
6 |
Is the test lamp blinking? | -- | Go to Step 14 | Go to Step 8 | ||||
7 |
Is the test lamp OFF? | -- | Go to Step 10 | Go to Step 17 | ||||
8 | Is the test lamp always ON? | -- | Go to Step 9 | Go to Step 11 | ||||
9 | Test the ratio control motor B1 low control circuit for a short to ground between the TCM C2 64-way connector 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 19 | Go to Step 18 | ||||
10 | Test the ratio control motor B1 low control circuit for a short to voltage between the TCM C2 64-way connector and the AT inline 20-way connector. Refer to Testing for a Short to Voltage and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 | ||||
11 | Connect a test lamp between the Ignition 1 voltage circuit and a good ground. Is the test lamp always ON? | -- | Go to Step 13 | Go to Step 12 | ||||
12 | Test the Ignition 1 voltage circuit for an open between the fuse block - underhood 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 19 | -- | ||||
13 | Test the ratio control motor B1 low control circuit for an open between the TCM C2 64-way connector 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 19 | Go to Step 15 | ||||
14 | Inspect for faulty connections at the transmission. Refer to Circuit Testing and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 17 | ||||
15 | Inspect for faulty connections at the TCM. Refer to Circuit Testing and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 19 | Go to Step 18 | ||||
16 | Replace the leadframe. The leadframe is part of the control solenoid valve assembly. Refer to Control Valve Body Assembly Disassemble . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||
17 | Replace the ratio control motor. The ratio control motor is part of the control solenoid valve assembly. Refer to Control Valve Body Assembly Disassemble . Did you complete the replacement? | -- | Go to Step 19 | -- | ||||
18 | Replace the TCM. Refer to Control Module References in Computer/Integrating Systems for replacement, set-up and programming. Did you complete the replacement? | -- | Go to Step 19 | -- | ||||
19 | Perform the following procedure in order to verify the repair:
Has the test run and passed? | -- | Go to Step 20 | Go to Step 2 | ||||
20 | 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? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |
