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For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2000 🢒 Eldorado 🢒 DTC 🢒 DTC P1634 Ignition 1 Switch Circuit

Refer to Engine Controls Schematics

PCM Power and Grounds


Object Number: 584716 Size: FS
Engine Controls Components
Information Sensors/Switches Description
MIL Control and DLC
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
PCM (BAT), A/C COMP, PARK/REV Fuses and A/C COMPRESSOR Relay
CRUISE, DIS, and PCM (IGN) Fuses
BATT 2 Fuse and Ignition Switch (2 of 2)
G102
 .

Circuit Description

The PCM receives three ignition inputs from the ignition switch: IGN 0, IGN 1, and CRANK Request. The PCM receives the IGN 1 input with the ignition switch in RUN and START. The PCM uses a class 2 ignition mode message, and the voltage input from two separate systems to test the IGN 1 circuit. If the PCM detects an improper IGN 1 input, 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 IGN 1 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 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

1

Did you perform the Powertrain On Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the 12 Volt Reference display on the scan tool.

Does the 12 Volt Reference display indicate FAULT?

--

Go to Step 3

Go to Diagnostic Aids

3

Inspect the Ignition 1 fuse.

Is the fuse open?

--

Go to Step 6

Go to Step 4

4
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector C1. Refer to Powertrain Control Module Replacement/Programming .
  3. Connect a test lamp between the IGN 1 circuit and chassis ground.
  4. Turn the ignition switch to the RUN, and START positions.

Is the test lamp ON with the ignition switch in the RUN and START position?

--

Go to Step 9

Go to Step 5

5

Is the test lamp ON for either ignition switch position?

--

Go to Step 10

Go to Step 7

6
  1. Test the following circuits for a short to ground:
    2. • Ignition 1 circuit
    • Crank Request circuit
  2. Refer to Circuit Testing and Wiring Repairs in Wiring Systems

Did you find and correct the condition?

--

Go to Step 12

Go to Step 10

7

Test for an open IGN 1 circuit. 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 Steering Column Lock and Ignition Switch Cylinder Replacement - On Vehicle in Steering Wheel and Column - Tilt.

Is the action complete?

--

Go to Step 12

--

11

Important: The replacement PCM must be programmed.

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 12

--

12
  1. Review and record the scan tool Fail Record data.
  2. Clear the DTC(s).
  3. Turn ON the ignition switch with the engine OFF.
  4. With the scan tool, observe the Specific DTC Information for DTC P1634 until the test runs.

Does the scan tool indicate that DTC P1634 passed?

--

System OK

Go to Step 2