Circuit Description
The powertrain control module (PCM) receives three ignition inputs from the ignition switch: ignition 0 signal, ignition 1 signal, and crank signal. The PCM receives the ignition 0 signal with the ignition switch in the CRANK position. The ignition switch sends this signal through the Off/Run/Crank voltage circuit. The PCM uses a Class II ignition mode message and voltage input from separate systems to test the Off/Run/Crank voltage circuit. If the PCM detects an improper ignition 0 signal, DTC P1633 will set.
Conditions for Running the DTC
No Class II serial data circuit problem.
Conditions for Setting the DTC
The PCM detects an improper IGN 0 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 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 Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | |||
1 | Did you perform the Diagnostic System Check-Engine Controls ? | Go to Step 2 | |
2 |
Does the test lamp illuminate with the ignition switch in both the ON and START positions? | Go to Step 6 | Go to Step 3 |
3 | Did the test lamp illuminate for either ignition switch position? | Go to Step 7 | Go to Step 4 |
4 | Test the Off/Run/Crank voltage circuit for an open and for a high resistance. Refer to Testing for Continuity and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 5 |
5 | Test for an intermittent and for a poor connection at the ignition switch. Refer to Testing for Intermittent Conditions and Poor Connections and Circuit Testing in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 7 |
6 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Circuit Testing in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
7 | Replace the ignition switch. Refer to Ignition and Start Switch Replacement in Instrument Panel, Gages and Console. Did you complete the replacement. | Go to Step 9 | -- |
8 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 9 | -- |
9 |
Does the DTC fail this ignition? | Go to Step 2 | Go to Step 10 |
10 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |
