GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2000 🢒 DeVille 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T80-E 🢒 Reverse Lockout System Inoperative

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Listen for an audible click when the reverse lockout relay operates. Command both the ON and OFF states. Repeat the commands as necessary. An audible click indicates that the relay is operating.

    2.

  2. Tests for voltage at the coil side of the reverse lockout relay.

    3.

  3. Verifies that the Dash Integration Module (DIM) is providing ground to the reverse lockout relay.

    4.

  4. Tests if ground is constantly being applied to the reverse lockout relay.

    5.

  5. Tests for voltage at the switch side feed circuit of the reverse lockout relay. The Reverse Lockout Fuse supplies power to the switch side feed circuit of the reverse lockout relay.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check - Auto Trans Shift Lock Control System?

--

Go to Step 2

Go to Diagnostic System Check - Automatic Transmission Shift Lock Control

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, navigate to the Dash Integration Module (DIM) Special Functions Output Controls Reverse Lockout screen. Command the reverse lockout drive ON and OFF.

Do you hear a click when you command the reverse lockout drive ON and OFF?

--

Go to Step 6

Go to Step 3

3

  1. Turn OFF the ignition.
  2. Disconnect the reverse lockout relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil side feed circuit of the reverse lockout relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 4

Go to Step 15

4

  1. Connect a test lamp between the coil side feed circuit of the reverse lockout relay and the coil side control circuit of the reverse lockout relay.
  2. With a scan tool, command the reverse lockout drive ON and OFF.

Does the test lamp turn ON and OFF with each command?

--

Go to Step 12

Go to Step 5

5

Does the test lamp remain illuminated with each command?

--

Go to Step 10

Go to Step 9

6
  1. Turn OFF the ignition.
  2. Disconnect the reverse lockout relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the switch side feed circuit of the reverse lockout relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 16

7
  1. Turn OFF the ignition.
  2. Reconnect the reverse lockout relay.
  3. Disconnect the reverse lockout actuator.
  4. Turn ON the ignition, with the engine OFF.
  5. Probe the control circuit of the reverse lockout actuator with a test lamp that is connected to a good ground.
  6. With a scan tool, command the reverse lockout drive ON.

Does the test lamp illuminate?

--

Go to Step 8

Go to Step 11

8
  1. Connect a test lamp between the B+ voltage supply circuit and the ground circuit of the reverse lockout actuator connector.
  2. With a scan tool, command the reverse lockout ON.

Does the test lamp illuminate?

--

Go to Step 14

Go to Step 17

9

Test the coil side control circuit of the reverse lockout relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 13

10

Test the coil side control circuit of the reverse lockout relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 13

11

Test the B+ voltage supply circuit of the reverse lockout actuator for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 12

12

Inspect for poor connections at the reverse lockout relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 18

13

Inspect for poor connections at the harness connector of the Dash Integration Module (DIM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 19

14

Important: Inspect the reverse lockout actuator for missing, broken, or mis-aligned parts.

Inspect for poor connections at the reverse lockout actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 21

Go to Step 20

15

Repair the coil side feed circuit of the reverse lockout relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 21

--

16

Repair the switch side feed circuit of the reverse lockout relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 21

--

17

Repair the ground circuit of the reverse lockout actuator. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 21

--

18

Replace the reverse lockout relay.

Did you complete the replacement?

--

Go to Step 21

--

19

Replace the DIM. Refer to Dash Integration Module Replacement in Body Control System.

Did you complete the replacement?

--

Go to Step 21

--

20

Important: Inspect the reverse lockout actuator for missing, broken, or mis-aligned parts.

Replace the reverse lockout actuator.

Refer to Transmission Control Replacement in Transmission Transaxle.

Did you complete the replacement?

--

Go to Step 21

--

21

Operate the vehicle within the Conditions for Running the symptom.

Did you correct the condition?

--

System OK

Go to Step 2