GM Service Manual Online
For 1990-2009 cars only

Circuit Description

Output driver modules (ODMs) are used by the powertrain control module (PCM) in order to turn on many of the current-driven devices that are needed to control various engine and transaxle functions. DTC P1585 set indicates that an improper voltage level has been detected on the output circuit which controls the cruise control inhibit circuit.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1585 Cruise Control Inhibit Output Circuit

Conditions for Running the DTC

    • The engine speed is 450 RPM or more.
    • System voltage is between 8-16 volts.

Conditions for Setting the DTC

    • The ignition is ON.
    • The PCM detects an improper voltage level on the cruise control inhibit signal circuit.
    • The condition exists for at least 30 seconds.

Action Taken When the DTC Sets

    • The PCM will not illuminate the malfunction indicator lamp (MIL).
    • The PCM will store the conditions present when the DTC sets as Fail Records data only.

Conditions for Clearing the DTC

    • The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
    • The DTC can be cleared by using the scan tools Clear DTC Information function.

Diagnostic Aids

In order to determine whether an improper voltage level exists on the output circuit, the PCM compares the voltage level to the commanded state.

If the condition is intermittent, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Normally, ignition positive voltage should be present on the signal circuit with the PCM disconnected and the ignition turned ON.

  2. Tests for a short to voltage on the control circuit.

  3. This vehicle is equipped with a PCM which utilizes an electrically erasable programmable read only memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

Step

Action

Value(s)

Yes

No

Schematic Reference: Cruise Control Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Turn OFF the ignition.
  2. Disconnect the powertrain control module (PCM) harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Using a DMM connected to a good ground, measure the voltage of the cruise control inhibit signal circuit.

Does the voltage measure near the specified value?

B+

Go to Step 3

Go to Step 4

3

  1. Turn OFF the ignition.
  2. Disconnect the cruise control module harness connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the cruise control inhibit signal circuit with a test lamp connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 7

Go to Step 5

4

Test the cruise control inhibit signal circuit for a short to ground.

Did you find and correct the condition?

--

Go to Step 10

Go to Step 6

5

Inspect for poor connections at the harness connector of the PCM. 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 10

Go to Step 8

6

Inspect for poor connections at the harness connector of the cruise control module. 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 10

Go to Step 9

7

Repair the short to voltage in the cruise control inhibit signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 10

--

8

Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 10

--

9

Replace the cruise control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 10

--

10

  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within normal cruise control operating conditions.

Does the DTC reset?

--

Go to Step 2

System OK