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For 1990-2009 cars only
Makes 🢒 Generic 🢒 2008 🢒 Unit Repair 🢒 Engine 🢒 Engine Controls and Fuel - Ram-Jet 🢒 Scan Tool Does Not Communicate with CAN Device

Diagnostic Instructions
    • Perform the Powertrain On Board Diagnostic (OBD) System Check --Performance Engine, or Powertrain On Board Diagnostic (OBD) System Check --Ram Jet Engine prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

CAN HI Circuit

1

1

--

--

CAN LO Circuit

1

1

--

--

1. Scan Tool Does Communicate

Circuit/System Description

The controller area network (CAN) HI and CAN LO circuits transmit information between the engine control module (ECM) and the scan tool.

The data link connector (DLC) is a standardized 16 cavity connector. The connector is designed to provide the following:

    • Scan tool power battery positive voltage at terminal 16
    • Scan tool ground at terminal 4
    • Common ground at terminal 5
    • CAN HI communication circuit at terminal 6
    • CAN LO communication circuit at terminal 14

Diagnostic Aids
    • The scan tool will power up with the ignition OFF.
    • The ECM will not communicate unless the ignition is ON.
    • It may be necessary to disconnect each module connected to the CAN communication circuits in order to isolate the condition.
    • No communication with the ECM can be caused by the following:
       - An open CAN communication circuit between the splice and the ECM
       - An ECM that is not powered up. Test the B+, ignition feed, and ground circuits for an open or short to ground

Reference Information

Schematic Reference

Data Communication Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views --Performance Engine
    •  Engine Controls Connector End Views --Performance Engine
    •  Engine Control Module Connector End Views --Ram Jet Engine
    •  Engine Controls Connector End Views --Ram Jet Engine

Engine Control Module Connector End Views

Description and Operation

Data Link Communications Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

    •  Engine Control Module Scan Tool Information --Performance Engine for scan tool information.
    •  Engine Control Module Scan Tool Information --Ram Jet Engine for scan tool information.

Circuit/System Verification

Ignition ON, attempt to establish communication with the ECM. The scan tool should display ECM information.

Circuit/System Testing
  1. Attempt to start the engine. The engine should start and idle.
    2. ⇒If the engine does not start and idle perform the following:
    1.1. Ignition OFF, disconnect the ECM harness connectors.
    1.2. Test for less than 5 ohms between the ground circuit terminals X2-73, X3-73, and ground.
    ⇒If greater than the specified range, repair the circuit for an open/high resistance.
    1.3. Ignition ON, verify that B+ is available at the ECM ignition voltage circuit terminals X1-19 and X1-10.
    ⇒If less than the specified range, refer to Ignition Relay Diagnosis --Performance Engine, or Powertrain Relay Diagnosis --Ram Jet for further diagnosis.
    1.4. Test for B+ at the ECM Battery voltage circuit terminal X1-20.
    ⇒If less than the specified range, repair the circuit for a short to ground, or an open/high resistance.
    1.5.  If all circuits test normal, replace the ECM.
  2. Ignition OFF, verify a test lamp does not illuminate between the following data link connector CAN circuit terminals and B+.
    3. • CAN HI Terminal 6
    • CAN LO Terminal 14
    ⇒If the test lamp illuminates, disconnect each module connected to the CAN circuit one at a time while observing the test lamp. If the test lamp does not illuminate when a module is disconnected replace the module. If the test lamp remains illuminated, repair the appropriate circuit for a short to ground.
  3. Ignition ON, test for 2-4 volts between the following data link connector CAN circuit terminals and ground.
    4. • CAN HI Terminal 6
    • CAN LO Terminal 14
    ⇒If less than the specified range, repair the appropriate circuit for an open. If the circuit tests normal replace the ECM.
    ⇒If greater than the specified range, test the appropriate circuit for a short to voltage. If the circuit tests normal replace the ECM.
  4. If all circuits test normal, refer to the scan tool user guide.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

Diagnostic Repair Verification for engine control module replacement, setup, and programming