GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 Vibe - FWD 🢒 DTC 🢒 DTC B2797

Circuit Description

A communication error may occur between the transponder key amplifier and transponder key ECU assembly when two or more ignition keys are positioned to close to each other or when there is noise in the communication line. Either one of these errors will cause DTC B2797 to set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC B2797 Communication Malfunction No. 1

Conditions for Running the DTC

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

Conditions for Setting the DTC

The ignition keys are positioned too close to each other, or noise occurs in the communication line.

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?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Is the ignition key near another ignition key or key ring is in contact with key ring?

--

Go to Step 3

Go to Step 4

3

  1. Separate the keys from each other or remove the key ring.
  2. Delete the DTC.
  3. Insert a key into the ignition cylinder, remove it. Perform this for all the other keys.

Does DTC reset.

--

Go to Step 4

Go to Step 9

4
  1. Disconnect the transponder key amplifier and the transponder key ECU assembly connectors.
  2. Measure the resistance between the transponder key amplifier and transponder key ECU assembly as follows:
    3. • ECU terminal 15 to amplifier terminal 4
    • ECU terminal 15 to ground

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

ECU to amplifier Less = 1 Ohm

ECU to ground Greater = 10 Kohms

Go to Step 6

Go to Step 5

5

Test the code circuit 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 9

Go to Step 6

6

Install a known good transponder key amplifier and check that the engine starts.

Does the engine start?

--

Go to Step 7

Go to Step 8

7

Replace the transponder key amplifier.

Did you complete the replacement?

--

Go to Step 9

--

8

Replace the transponder key ECU assembly.

Did you complete the replacement?

--

Go to Step 9

--

9
  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