GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Cobalt 🢒 Restraints 🢒 SIR 🢒 DTC P1633

Circuit Description

The engine control module (ECM)/powertrain control module (PCM) receives 2 ignition inputs from the ignition switch, ignition 1 signal, and ignition accessory signal. The ECM/PCM receives the crank input from a serial data message from the body control module (BCM). The ECM/PCM determines the state of the ignition switch based on these 3 inputs. If the ECM/PCM detects an improper ignition accessory signal, DTC P1633 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1633 Ignition 0 Switch Circuit

Conditions for Running the DTC

No serial data circuit problem.

Conditions for Setting the DTC

The ECM/PCM detects an improper ignition accessory input voltage.

Action Taken When the DTC Sets
    • The ECM/PCM will not illuminate the malfunction indicator lamp (MIL).
    • The ECM/PCM will store conditions which were present when the DTC set as Failure Records 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 tool Clear DTC Information function.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics in Engine Controls 2.0L or Engine Controls Schematics in Engine Controls 2.2L (L61)

Connector End View Reference: Powertrain Control Module Connector End Views in Engine Controls 2.0L or Engine Control Module Connector End Views in Engine Controls 2.2L (L61)

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 ON the ignition, with the engine OFF.
  2. With a scan tool observe the Ignition Accessory Signal parameter in the Engine Data list.

Does the scan tool display ON?

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

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM)/powertrain control module (PCM).
  3. Connect a test lamp between the accessory voltage circuit of the ECM/PCM and a good ground.
  4. Turn the ignition switch to the Accessory and ON positions.

Does the test lamp illuminate with the ignition switch in both the Accessory and ON positions?

Go to Step 5

Go to Step 4

4

Repair the accessory voltage circuit of the ECM/PCM for an open or for a high resistance. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 7

--

5

Inspect for poor connections at the harness connector of the ECM/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 7

Go to Step 6

6

Important: The replacement ECM/PCM must be programmed.

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

Did you complete the replacement?

Go to Step 7

--

7
  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records.

Does the DTC fail this ignition?

Go to Step 3

System OK