GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2004 🢒 DeVille 🢒 DTC 🢒 DTC P0512

Circuit Description

The powertrain control module (PCM) receives two ignition inputs from the ignition switch: IGN 0 and IGN 1. The PCM receives the Crank Request input with the ignition switch in the START position. The PCM uses a class 2 ignition mode message, and the voltage input from two separate systems to test the Crank Request circuit. If the PCM detects an improper input, DTC P0512 will set.

Conditions for Running the DTC

No Class 2 serial data circuit problem.

Conditions for Setting the DTC

The PCM detects an improper Crank Request input.

Action Taken When the DTC Sets
    • The PCM will not illuminate the malfunction indicator lamp (MIL).
    • The PCM will store conditions which were present when the DTC set as Fail Records information only.

Conditions for Clearing the MIL/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 tool Clear DTC Information function.

Step

Action

Yes

No

Schematic References: Starting and Charging Schematics

Connector End View Reference: Engine Controls Connector End Views in Engine Controls-4.6L or Power and Grounding Connector End Views in Wiring Systems

1

Did you perform the Engine Electrical Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Engine Electrical

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the Crank Request parameter in the PCM data list .

Does the Crank Request parameter display No?

Go to Step 3

Go to Step 4

3
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the Crank Request parameter in the PCM data list .
  3. Turn the ignition to the START positions.

Does the Crank Request parameter display Yes?

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 5

4
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector.
  3. Connect test lamp between the Crank Request circuit and ground.
  4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

Go to Step 6

Go to Step 9

5
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector.
  3. Connect test lamp between the Crank Request circuit and ground.
  4. Turn the ignition to the start position.

Does the test lamp illuminate?

Go to Step 9

Go to Step 7

6

Test the Crank Request circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

7

Test the Crank Request circuit for a high resistance or open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

8

Inspect for poor connections at the ignition switch. 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 12

Go to Step 10

9

Inspect for poor connections at 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 12

Go to Step 11

10

Replace the ignition switch. Refer to Ignition and Start Switch Replacement in Steering Wheel and Column.

Did you complete the replacement?

Go to Step 12

--

11

Important: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls-4.6L.

Is the action complete?

Go to Step 12

--

12
  1. Review and record the scan tool Fail Record data.
  2. Clear the DTCs.
  3. Turn ON the ignition, with the engine OFF.
  4. With the scan tool, observe the Specific DTC Information for DTC P0512 until the test runs.

Does the scan tool indicate that DTC P0512 passed?

System OK

Go to Step 2