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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 HHR 🢒 Power and Signal Distribution 🢒 Data Communications 🢒 Scan Tool Does Not Communicate with Class 2 Device

Circuit Description

The powertrain control module (PCM) is connected to the class 2 serial data circuit. The class 2 serial data circuit is used for diagnostic purposes only in this vehicle. Connecting a scan tool to the data link connector (DLC) allows communication with the PCM for diagnostic purposes. DTCs may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

Diagnostic Aids

The PCM is the only module on the class 2 serial data buss on this vehicle. The most likely cause of the buss failure will be a short or open.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. A partial loss or intermittent loss of communication in the class 2 serial data circuit uses a different procedure than a total loss of communication of the class 2 serial data circuit.

    2.

  2. If there are no current DTCs that begin with the letter "U", the communication concern has been repaired.

    3.

  3. The communication concern may have prevented diagnosis of the customer complaint.

Step

Action

Yes

No

Schematic Reference: Data Communication Schematics

Connector End View Reference: Master Electrical Component List

1

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up

2

  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to communicate with the powertrain control module (PCM) on the class 2 serial data circuit.

Does the scan tool communicate with PCM on the class 2 serial data circuit?

Go to Testing for Intermittent Conditions and Poor Connections

Go to Step 3

3
  1. Turn the ignition OFF.
  2. Remove the scan tool from the data link connector (DLC).
  3. Remove the harness connector from the PCM that contains the class 2 serial data connector.
  4. Test for an open between the DLC terminal 2 and the terminal on the PCM harness connector that contains the class 2 serial data circuit.

Did you find and correct the condition?

Go to Step 9

Go to Step 4

4

Important: Turn ON the ignition, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions.

Test the class 2 serial data circuit for a short to ground or a short to voltage. Refer to Circuit Testing .

Did you find and correct the condition?

Go to Step 9

Go to Step 5

5

  1. Turn OFF the ignition.
  2. Inspect for poor connections and terminal tension at the DLC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 9

Go to Step 6

6

Test the signal ground circuits of the DLC for an open or high resistance. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .

Did you find and correct the condition?

Go to Step 9

Go to Step 7

7

Inspect for poor connections and terminal tension at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Wiring Repairs .

Did you find and correct the condition?

Go to Step 9

Go to Step 8

8

Important: Perform the module setup procedure if required. Refer to Control Module References .

Replace the suspect module. Refer to Control Module References for the appropriate Repair Instructions for module replacement.

Did you complete the replacement?

Go to Step 9

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9
  1. Connect the PCM.
  2. Connect all the connectors.
  3. Install a scan tool.
  4. Turn ON the ignition leaving the engine OFF.

    5. Important: The scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn OFF or disconnect the scan tool before you display DTCs.

  5. Wait for 10 seconds.
  6. Select the display DTCs function for the PCM. If using a Tech 2, use the Class 2 DTC Check feature in order to determine if the PCM has DTCs set.
  7. Record all of the displayed DTCs and the DTC status.

Did your record any DTCs which begin with a letter "U" and with a current status?

Go to Step 11

Go to Step 10

10

Did you record any DTCs which do not begin with a letter "U"?

Go to Step 11

Go to Step 13

11

Diagnose the DTCs as directed by the diagnostic procedures for the particular concern.

Did you complete the action?

Go to Step 12

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12

Did you diagnose all of the DTCs?

Go to Step 13

Go to Step 11

13

Clear the DTCs using the scan tool.

Did you complete the action?

System OK

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