GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 Vibe - FWD 🢒 Safety and Security 🢒 Immobilizer 🢒 DTC B2780

Circuit Description

The transponder key ECU assembly monitors the status of the unlock warning switch. The transponder key ECU assembly detects when the unlock warning switch is ON. If the transponder key ECU assembly does not detect the unlock warning switch ON even when the key is in the ignition switch, DTC B2780 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2780 Push Switch/Key Unlock Warning Switch Malfunction

Conditions for Running the DTC

This DTC shall run when key is inserted into key cylinder.

Conditions for Setting the DTC

The unlock warning switch does not detected when ignition switch is ON.

Action Taken When the DTC Sets

The engine will not start.

Conditions for Clearing the DTC

The DTC will clear when conditions for setting the DTC have been repaired.

Step

Action

Value(s)

Yes

No

Schematic Reference: Immobilizer Schematics

Connector End View Reference: Immobilizer Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

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Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With the scan tool, observe the Key in Ignition parameter in the Immobilizer data list.

Does the Key in Ignition parameter display Yes?

--

Go to Step 3

Go to Step 9

3

  1. Turn OFF ignition.
  2. Disconnect the unlock warning switch assembly harness connector.
  3. Remove the unlock warning switch assembly.
  4. Measure the resistance between terminal 1 and terminal 2 of the unlock warning switch assembly while depressing and releasing the switch actuator.

Is the resistance measured less than or greater than the specified value?

Depressed = less than 1 ohm

Released = 10 kohms or greater

Go to Step 4

Go to Step 8

4

Measure the resistance between the unlock warning switch assembly harness connector terminal 1 and a good ground.

Does the resistance measure less than the specified value?

1 Ohm

Go to Step 5

Go to Step 6

5
  1. Disconnect the transponder key ECU assembly harness connector.
  2. Measure the resistance as follows:
    3. • Between transponder key ECU harness connector terminal 3 and unlock warning switch assembly harness connector terminal 2.
    • Between the unlock warning switch assembly harness connector terminal 2 and a good ground.

Is the resistance measured in the step above between the transponder key ECU harness connector terminal 3 and unlock warning switch assembly harness connector terminal 2 less than 1 ohm and between the unlock warning switch assembly harness connector terminal 2 and a good ground 10 kohms or greater?

--

Go to Step 10

Go to Step 7

6

Test the unlock warning switch ground circuit for an open/high resistance. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 10

Go to Step 8

7

Test the circuits for an open/high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 10

Go to Step 9

8

Replace the unlock warning switch assembly .

Did you complete the replacement?

--

Go to Step 10

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9

Replace the transponder key ECU assembly.

Did you complete the replacement?

--

Go to Step 10

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10
  1. Use the scan tool in order to clear the DTC.
  2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK