GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Chevy P42 Commercial Chassis 🢒 Engine 🢒 Engine Controls - 6.5L (L57) 🢒 Data Link Connector Diagnosis

Go to Engine Controls Schematic

Cell 23: PCM Power and Grounding, MIL, and DLC


Object Number: 380028 Size: FS
Engine Controls Components L57 EFI
Powertrain Control Module Description
Cell 23: Glowplug Control (California)
OBD II Symbol Description Notice
Cell 81: Indicators
Cell 11: Gauges fuse
Cell 10: Ignition Switch and Fuse Block
Handling ESD Sensitive Parts Notice
Cell 10: Fuse Block and Headlamp Switch
Cell 11: ECM-BAT and ENG-BAT fuses
Handling ESD Sensitive Parts Notice
Cell 44: Diesel, ABS Power and Grounding, DLC Output
Cell 14: G200
Cell 14: S110 [L57]
Cell 14: G108 [L57]
 .

Circuit Description

There should always be a steady Malfunction Indicator Lamp (MIL) when the ignition is ON and engine OFF. Battery ignition voltage is supplied to the lamp. The PCM will turn the lamp ON by grounding the ignition feed circuit.

Test Description

The number(s) below refer to the step number(s) on the Diagnostic Table.

  1. This step verifies if the problem is in the scan tool or the vehicle.

    2.

  2. If the resistance reading is below 10 ohms, this indicates that the Serial Data circuit or a Controller Module that shares the same circuit is shorted to ground or shorted internally.

    3.

  3. By disconnecting each Controller Module that shares the Serial Data circuit and re-checking the resistance can determine if the shared Controller Module is shorted internally.

    4.

  4. The step checks to determine if the Serial Data circuit is shorted to voltage.

    5.

  5. A resistance reading under 10 ohms indicates that the circuit has continuity. A high resistance reading indicates an open in the circuit.

Step

Action

Value(s)

Yes

No

1

Did the Powertrain On-Board Diagnostic (OBD) System Check performed?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Disconnect the scan tool from the vehicle.
  2. Connect the scan tool to a vehicle with the same model year and with the same systems.
  3. Turn the ignition ON leaving the engine OFF.

Does the PCM communicate with the scan tool?

--

Go to Step 3

Go to Step 4

3
  1. Reconnect the scan tool to the original vehicle.
  2. Turn the ignition ON leaving the engine OFF.

Does the scan tool communicate with the PCM?

--

Go to Step 11

Go to Step 5

4

The scan tool may be malfunctioning. Refer to the scan tool instruction manual.

Is the action complete?

--

Go to Step 17

--

5

  1. Turn the ignition OFF.
  2. Disconnect the PCM connectors.
  3. With a J 39200 DMM , measure the resistance at the DLC connector between terminal 4 and terminal 2.

Is the resistance less than the specified value?

10 Ohms

Go to Step 6

Go to Step 7

6

  1. Disconnect the Electronic Brake Control Module (EBCM).
  2. Measure the resistance at the DLC connector between terminal 4 and terminal 2.
  3. Repeat the procedure for the following shared Modules on the Serial Data circuit.(if equipped)
    4. • Power Steering Control Module(if equipped)
    • EVO Module
    • Automatic Transfer Case (ATC) Module (if equipped)

Does disconnecting one of the Modules cause the resistance to be greater than the specified value?

10 Ohms

Go to Step 15

Go to Step 14

7

  1. Turn the ignition ON leaving the engine OFF.
  2. With the J 39200 DMM, measure the voltage at the DLC connector between terminal 4 and terminal 2.

Is the voltage less than the specified value?

1.0 V

Go to Step 8

Go to Step 12

8

  1. Turn the ignition OFF.
  2. With the J 39200 DMM, measure the resistance between the DLC connector terminal 2 and the Serial Data circuit terminal at the PCM connector.

Is the resistance less than the specified value?

10 Ohms

Go to Step 9

Go to Step 13

9
  1. Check all the power and ground circuits to the PCM for opens and short to grounds. Refer to Wiring Repairs in Wiring Systems.
  2. If a problem is found, repair the problem as necessary.

Did you perform a repair?

--

Go to Step 17

Go to Step 10

10
  1. Check for proper connections at the PCM. Refer to Wiring Repairs in Wiring Systems.
  2. If a problem is found, repair the problem as necessary.

Did you perform a repair?

--

Go to Step 17

Go to Step 16

11

Repair the intermittent short or open on the serial data circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 17

--

12

Repair the short to voltage on the serial data circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 17

--

13

Repair the open in the serial data circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 17

--

14

Repair the short to ground on the serial data circuit. Refer to Wiring Repairs in Wiring Systems.

Is the action complete?

--

Go to Step 17

--

15

Replace the appropriate module that caused the resistance increase.

Is the action complete?

--

Go to Step 17

--

16

Replace the PCM.

Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

--

Go to Step 17

--

17

Operate the vehicle within the conditions the symptom was noted.

Does the system operate properly?

--

Go to Powertrain On Board Diagnostic (OBD) System Check

Go to Step 2