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 1 signal with the ignition switch in the ON and START positions. The PCM uses a Class II ignition mode message and voltage input from the ignition switch to test the ignition 1 voltage circuit. If the PCM detects an improper ignition 1 signal, DTC P1634 will set.
Conditions for Running the DTC
No class 2 serial data circuit problem.
Conditions for Setting the DTC
The PCM detects an improper ignition 1 voltage signal.
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 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 | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check - Engine Electrical? | -- | Go to Step 2 | |
2 |
Is the ignition 1 signal near the specified value? | 12 V | Go to Step 4 | Go to Step 3 |
3 | Inspect the fuse to the ignition 1 voltage circuit. Is the fuse open? | -- | Go to Step 11 | Go to Step 4 |
4 |
Does the test lamp illuminate with the ignition switch in the ON and START position? | -- | Go to Step 17 | Go to Step 5 |
5 | Did the test lamp illuminate for either ignition switch position? | -- | Go to Step 18 | Go to Step 6 |
6 |
Does the test lamp illuminate? | -- | Go to Step 7 | Go to Step 12 |
7 |
Does the test lamp illuminate? | -- | Go to Step 8 | Go to Step 10 |
8 |
Does the test lamp illuminate? | -- | Go to Step 16 | Go to Step 9 |
9 | Connect a test lamp between the control circuit of the ignition 1 relay and a good ground. Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 13 |
10 | Test the ignition 1 voltage circuit for an open and for a high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- |
11 | Test the ignition 1 voltage circuit and the voltage circuit of the start 1 relay for a short to ground. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 20 |
12 | Test the ignition 1 relay battery positive voltage circuit for an open and for a high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- |
13 | Test the ignition 1 relay control circuit for an open and for a high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | Go to Step 15 |
14 | Test the ignition 1 relay ground circuit for an open and for a high resistance. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 21 | -- |
15 | Test for an intermittent and for a poor connection 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 21 | Go to Step 18 |
16 | Test for an intermittent and for a poor connection at the ignition 1 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 19 |
17 | Test for an intermittent and for a poor connection 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 21 | Go to Step 20 |
18 | Replace the ignition switch. Refer to Ignition and Start Switch Replacement in Steering Wheel and Column. Did you complete the replacement? | -- | Go to Step 21 | -- |
19 | Replace the ignition 1 relay. Refer to Relay Replacement in Wiring Systems. Did you complete the replacement? | -- | Go to Step 21 | -- |
20 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | -- | Go to Step 21 | -- |
21 |
Does the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 22 |
22 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |
