For 1990-2009 cars
Automatic Transmission Components
Automatic Transmission Controls Schematics
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The TCM sends a Pulse Width Modulated (PWM) signal to the ABS controller. The signal pulse width corresponds to the actual gear in which the transmission is currently operating. If a circuit fault is detected by the TCM, this DTC will set.

### Conditions For Running The DTC

Tests continuously

### Conditions for Setting the DTC

The TCM detects an open, short to ground, or short to B+ on the output circuit.

### Action Taken When the DTC Sets

• | The MIL/STL will not illuminate.

• | The TCM memory stores the DTC at the time of the first failure.

### Conditions for Clearing the MIL/DTC

• | A History DTC clears after forty consecutive warm-up cycles if no failures are present by this or any other non-emission related diagnostic.

• | The scan tool clears the MIL/DTC.

### Diagnostic Aids

Use the Connector Test Adapter Kit J 35616-A for any test that requires probing the TCM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

Check for the following conditions:

• | Poor connections at the TCM or at the component. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Engine Electrical, Troubleshooting Procedures, Checking Terminal Contact for proper procedure.

• | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving any related connectors and any wiring harnesses. A change in the display may help to locate the fault.

### Test Description

The number(s) below refer to the step number(s) on the Diagnostic Table.

1. Check the circuit for the following conditions which may cause an intermittent problem:

• | Poor connections at the ECM or TCM. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Engine Electrical, Troubleshooting Procedures, Checking Terminal Contact for proper procedure.

• | Misrouted harness. Inspect the harness to ensure that the harness is not routed too close to high voltage wires such as spark plug leads, or too close to high current devices such as the alternator, motors, solenoids etc.

• | Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while any related connectors and any wiring harnesses. A change in the display may help to locate the fault.

#### DTC P1845 - Transmission Gear Ratio Output Circuit

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn off the ignition.
2. Disconnect the TCM.
3. Turn on the ignition with the engine off.
4. Use the DVM J 39200 in order to measure the voltage on the Transmission Torque Reduction Request Circuit at the TCM harness connector.

Does the DVM indicate the specified voltage?

B+

Go to Step 5

Go to Step 3

3 |

1. Turn off the ignition.
2. Disconnect the ABS controller.
3. Use the DVM J 39200 in order to check the harness for continuity on the Transmission Gear Ratio Output Circuit from the ABS controller to the TCM.

Is the continuity indicated?

--

Go to Step 4

Go to Step 6

4 | Use the DVM J 39200 in order to check the continuity between the Transmission Gear Ratio Output Circuit and ground. Is the continuity indicated? | -- | Go to Step 7 | Go to Step 9
5 | Use the test light J 34142-B connected to ground in order to probe the Transmission Gear Ratio Output Circuit at the TCM harness connector. Does the test light illuminate? | -- | Go to Step 8 | Go to Step 10
6 | Repair the open or high resistance in the circuit. Is the action complete? | -- | Go to Step 11 | --
7 | Repair the circuit shorted to ground. Is the action complete? | -- | Go to Step 11 | --
8 | Repair the circuit shorted to B+ Is the action complete? | -- | Go to Step 11 | --
9 | Check the ABS controller harness for a poor connection or poor terminal tension. Refer to Engine Electrical, Troubleshooting Procedures, Checking Terminal Contact for proper procedure. Was a problem found and corrected? | -- | Go to Step 11 | Go to Antilock Brake System (ABS)
10 | Check the TCM harness connector for a poor connection or poor terminal tension. Refer to Engine Electrical, Troubleshooting Procedures, Checking Terminal Contact for proper procedure. Was a problem found and corrected? | -- | Go to Step 11 | Go to Test Description
11 |

1. Clear the DTCs with the scan tool.
2. Turn off the ignition for 15 seconds.
3. Start the engine.
4. Operate the vehicle within the conditions required for this diagnostic to run. Refer to Conditions for Running the DTC.
5. Check for any DTCs.

Is DTC P1845 set?

--

Go to Step 2

Go to Step 12

12 | Were there any additional DTCs noted during the Powertrain or Transmission OBD System Check that have not been diagnosed? | -- | Go to the applicable DTC table | Go to Step 13
13 | Does the Transmission now function properly? | -- | System OK | Go to Functional Test