GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 1999 🢒 S/T Isuzu - 2WD 🢒 Engine 🢒 Engine Controls - 2.2L 🢒 Data Link Connector Diagnosis

Object Number: 387307 Size: LF
Engine Controls Components
Cell 20: Power, Grounding, Generator and MIL
OBD II Symbol Description Notice
Powertrain Control Module Connector End Views
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The provision for communicating with the control module is the Data Link Connector (DLC). It is usually located under the instrument panel. The DLC is used to connect to a scan tool. Some common uses of the scan tool are listed below:

    • Identifying stored Diagnostic Trouble Codes (DTCs).
    • Clearing DTCs.
    • Performing output control tests.
    • Reading serial data.

Battery power and ground is supplied for the scan tool through the DLC. The Class 2 serial data circuit to the DLC allows the PCM to communicate with the scan tool. The Class 2 serial data circuit is also used to communicate with the Electronic Brake Control Module (EBCM), and the Truck Body Control Module.

Diagnostic Aids

Ensure that the correct application--the model year, the car line, and the VIN code--has been selected on the scan tool. If communication still cannot be established, try the scan tool on another vehicle to ensure that the scan tool or the cables are not the cause of the condition.

An intermittent may be caused by the following:

    • Poor connection
    • Rubbed-through wire insulation
    • Broken wire inside the insulation

Any circuitry that is suspected of causing an intermittent complaint should be thoroughly checked for the following conditions:

    • Backed-out terminals
    • Improper mating of terminals
    • Broken locks
    • Improperly formed or damaged terminals
    • Poor terminal-to-wiring connections
    • Physical damage to the wiring harness
    • Corrosion

Test Description

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

  1. The Powertrain OBD System Check prompts you to complete some of the basic checks and to store the freeze frame data and the failure records on the scan tool if applicable. This creates an electronic copy of the data captured when the malfunction occurred. The scan tool stores this data for later reference.

    2.

  2. Check for proper voltage supply in the DLC.

    3.

  3. Locate and repair any shorts that may have caused the fuse to open before replacing the fuse, if the no voltage conditions was due to an open fuse.

    4.

  4. Reprogram the replacement PCM and perform the crankshaft position system variation learn procedure. Refer to the latest Isuzu Technical Communications System (ITCS) information for PCM programming and the Crankshaft Position System Variation Learn for the crankshaft position system variation learn procedure.

  5. The scan tool or the associated cables could be malfunctioning. Refer to the scan tool manual for repair information.

    6.

  6. If the serial data loss occurred after a good theft password has been received, the PCM will allow the vehicle to start on following attempts. After making the necessary repairs to the vehicle, reprogram the PCM and complete the password learn procedure and the crankshaft position system variation procedures in order to allow the theft system to operate properly. Refer to the Crankshaft Position System Variation Learn for the reprogramming procedures and the crankshaft position system variation learn procedure.

Data Link Connector Diagnosis

Step

Action

Value(s)

Yes

No

1

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

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2
  1. Turn ON the ignition switch leaving the engine OFF.
  2. Observe the Malfunction Indicator Lamp (MIL).

Is the MIL ON?

--

Go to Step 3

Go to Malfunction Indicator Lamp (MIL) Inoperative

3

Install a scan tool.

Does the scan tool power up?

--

Go to Step 4

Go to Step 6

4

Attempt to communicate with the following control modules with the scan tool:

    • Body Control Module (BCM)
    • Electronic Brake Control Module (EBCM)

Does the scan tool communicate with the control modules?

--

Go to Step 11

Go to Step 5

5
  1. Turn OFF the ignition switch.
  2. Disconnect the PCM electrical connectors.
  3. Turn ON the ignition switch leaving the engine OFF.
  4. Attempt to communicate with the following control modules with the scan tool:
  5. Body Control Module (BCM)
  6. Electronic Brake Control Module (EBCM)

Does the scan tool communicate with the control modules?

--

Go to Step 13

Go to Step 12

6

  1. Connect a DMM to ground.
  2. Probe the DLC battery feed circuit terminal (cavity 16).

Is the voltage near the specified value?

B+

Go to Step 7

Go to Step 8

7
  1. Connect a DMM to B+.
  2. Probe the DLC ground circuit terminals (cavities 4 and 5).

Is the voltage near the specified value?

B+

Go to Step 9

Go to Step 10

8

Repair the following condition(s) in the battery feed circuit: Refer to Wiring Repairs in Wiring Systems.

    • Poor electrical connection
    • Open in the circuit
    • Short to ground

Is the action complete?

--

Go to Step 16

--

9
  1. Check the DLC electrical terminals for the following conditions:
    2. • Proper terminal tension
    • Excessive resistance
    • Backed out terminals
    • Open in the Battery Feed fuse
  2. Repair the terminals as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 16

Go to Step 15

10

Repair the following condition(s) in the DLC ground circuit(s) at the PCM and DLC connection: Refer to Wiring Repairs in Wiring Systems.

    • Poor electrical connection(s)
    • Open in the circuit

Is the action complete?

--

Go to Step 16

--

11
  1. Check for the following condition(s) in the Class 2 Serial data line from the splice to the PCM:
    2. • Poor electrical connection
    • Open in the circuit
  2. Repair the condition(s) as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 16

Go to Step 13

12
  1. Check for the following condition(s) in the Class 2 Serial data line from the DLC to the PCM:
    2. • Short to voltage
    • Short to ground
    • Open circuit
    • Poor electrical connection
  2. Repair the condition(s) as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

--

Go to Step 16

Go to Step 14

13

  1. Turn OFF the ignition switch.
  2. Replace the PCM. Refer to the Powertrain Control Module Replacement .

Is the action complete?

--

Go to Step 16

--

14
  1. Install the scan tool on another vehicle with Class 2 serial data.
  2. Check for a proper operation of the scan tool.

Does the scan tool work properly on a different vehicle?

--

Go to Electrical Diagnosis

Go to Step 15

15

The scan tool is malfunctioning. Refer to the scan tools manual for repair information. Is the action complete?

--

Go to Step 16

--

16

  1. The PCM may need to be reprogrammed. Refer to Powertrain Control Module Replacement/Programming for the reprogramming procedure.
  2. Perform the Crankshaft Variation Learn Procedure. Refer to Crankshaft Position System Variation Learn .
  3. Using a scan tool, clear the DTCs.
  4. Attempt to start the engine.

Does the engine start and continue to run?

--

Go to Step 17

Go to Step 2

17
  1. Idle the engine until the normal operating temperature is reached.
  2. Check to see if any DTCs are set.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Applicable DTC Table

System OK