GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1997 🢒 Catera 🢒 Body and Accessories 🢒 Wiring Systems 🢒 Scan Tool Does Not Communicate with Engine Control Module

Step

Action

Value(s)

Yes

No

1

Was the Data Link Connector System Check performed?

--

Go to Step 2

Go to Data Link Communications System Check .

2

Attempt to establish communication with the same system, same year, on a different vehicle.

Can communication be established?

--

Go to Step 4

Go to Step 3

3
  1. The scan tool may be inoperative.
  2. Verify that the scan tool operates properly.

Does the scan tool operate properly?

--

Go to Step 4

Go to Scan Tool Inoperative .

4
  1. Disconnect the engine control module connector.
  2. Use the DMM to measure the resistance between terminal 88 of the engine control module connector and terminal 7 of the data link connector.

Is the measured resistance within the specified value?

Less than 5 ohms

Go to Step 6

Go to Step 5

5
  1. Locate an open or a high resistance in circuits XM101, XM100 and/or XM88.
  2. Repair the open or the high resistance in circuits XM101, XM100 and/or XM88.

Is the repair complete?

--

Go to Step 23

--

6

Use the DMM to measure the resistance between terminal 7 of the data link connector and a known good ground.

Is the measured resistance within the specified value?

Less than 5 ohms

Go to Step 7

Go to Step 14

7
  1. Disconnect the instrument cluster connector.
  2. Use the DMM to measure the resistance between terminal 7 of the data link connector and a known good ground.

Is the measured resistance within the specified value?

Less than 5 ohms

Go to Step 9

Go to Step 8

8
  1. There is an internal failure within the instrument cluster that is pulling the circuit to ground.
  2. Replace the instrument cluster. Refer to Instrument Cluster Gage Replacement in Instrument Panel, Gauges and Console.

Is the replacement complete?

--

Go to Step 23

--

9
  1. Disconnect the driver seat adjuster memory module.
  2. Use the DMM to measure the resistance between terminal 7 of the data link connector and a known good ground.

Is the measured resistance within the specified value?

Less than 5 ohms

Go to Step 11

Go to Step 10

10
  1. There is an internal failure within the driver seat adjuster memory module that is pulling the circuit to ground.
  2. Replace the driver seat adjuster memory module. Refer to Memory Seat Control Module Replacement in Seats.

Is the replacement complete?

--

Go to Step 23

--

11
  1. Disconnect the transmission control module.
  2. Use the DMM to measure the resistance between terminal 7 of the data link connector and a known good ground.

Is the measured resistance within the specified value?

Less than 5 ohms

Go to Step 13

Go to Step 12

12
  1. There is an internal failure within the transmission control module that is pulling the circuit to ground.
  2. Replace the transmission control module. Refer to Transmission Control Module Replacement in Automatic Transmission.

Is the replacement complete?

--

Go to Step 23

--

13

If all of the modules are disconnected and there is still a short to ground, locate and repair a short to ground in the circuits.

Is the repair complete?

--

Go to Step 23

--

14

Use the DMM to measure the voltage between terminal 7 of the data link connector and a known good ground.

Is the measured voltage within the specified value?

B+

Go to Step 15

Go to Step 22

15
  1. Disconnect the instrument cluster connector.
  2. Use the DMM to measure the voltage between terminal 7 of the data link connector and a known good ground.

Is the measured voltage within the specified value?

B+

Go to Step 16

Go to Step 17

16
  1. There is an internal failure within the instrument cluster that is pulling the circuit to B+.
  2. Replace the instrument cluster. Refer to Instrument Cluster Gage Replacement in Instrument Panel, Gauges and Console.

Is the replacement complete?

--

Go to Step 23

--

17
  1. Disconnect the driver seat adjuster memory module.
  2. Use the DMM to measure the voltage between terminal 7 of the data link connector and a known good ground.

Is the measured voltage within the specified value?

B+

Go to Step 18

Go to Step 19

18
  1. There is an internal failure within the driver seat adjuster memory that is pulling the circuit to B+.
  2. Replace the driver seat adjuster memory module. Refer to Memory Seat Control Module Replacement in Seats.

Is the replacement complete?

--

Go to Step 23

--

19
  1. Disconnect the transmission control module.
  2. Use the DMM to measure the voltage between terminal 7 of the data link connector and a known good ground.

Is the measured voltage within the specified value?

B+

Go to Step 20

Go to Step 21

20

If all of the modules are disconnected and there is still a short to B+, locate and repair a short to B+ in the circuits.

Is the repair complete?

--

Go to Step 23

--

21
  1. There is an internal failure within the transmission control module that is pulling the circuit to B+.
  2. Replace the transmission control module. Refer to Transmission Control Module Replacement in Automatic Transmission.

Is the replacement complete?

--

Go to Step 23

--

22
  1. Use the DMM to check for proper voltage and ground circuits to the engine control module.
  2. If the voltage and ground circuits are OK, replace the engine control module. Refer to Engine Control Module Replacement/Programming in Engine Controls.

Is the replacement complete?

`

--

Go to Step 23

--

23
  1. Connect all connectors and components that were disconnected.
  2. Connect the scan tool.
  3. Establish communication with the engine control module.

Does the scan tool communicate with the engine control module?

--

System OK

Go to Step 1