GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you review the Audible Warnings Description and perform the necessary inspections?

--

Go to Step 2

Go to Diagnostic Starting Point

2

  1. Insert the key in the ignition.
  2. Turn the ignition switch to the OFF position.
  3. Using a scan tool, enter BCM Data List INPUT 1. Monitor the Key-In-Ignition input.

Is YES displayed?

--

Go to Step 3

Go to Step 6

3

Inspect the connections at the BCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Are the connections in need of repair?

--

Go to Step 4

Go to Step 5

4

Repair the connections at the BCM as necessary. Refer to Connector Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 14

--

5

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the repair?

--

Go to Step 14

--

6

  1. Using the DMM, backprobe C201 terminal B3 to ground.
  2. Insert the key in the ignition.
  3. Turn OFF the ignition.

Is the voltage near the specified value?

B+

Go to Step 7

Go to Step 12

7

  1. Using the DMM, backprobe C201 terminal B3 to terminal B4.
  2. Insert the key in the ignition.
  3. Turn OFF the ignition.

Is the voltage near the specified value?

B+

Go to Step 8

Go to Step 11

8

Inspect for an open or high resistance in CKT 750. Refer to Circuit Testing in Wiring Systems.

Was an open or high resistance found?

--

Go to Step 9

Go to Step 10

9

Repair the open or high resistance in CKT 750. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 14

--

10

Replace the key-in-ignition alarm switch.

Did you complete the replacement?

--

Go to Step 14

--

11

Locate and repair the open or high resistance in CKT 750. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 14

--

12

With a DMM connected to ground, backprobe the BCM connector C2 terminal B9 in CKT 80.

Is the voltage near the specified value?

B+

Go to Step 13

Go to Step 3

13

Locate and repair the open or high resistance in CKT 80. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 14

--

14

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2