GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 Envoy - 4WD 🢒 Restraints 🢒 SIR 🢒 Scan Tool Does Not Communicate with UART Data Line

Step

Action

Value(s)

Yes

No

1

Was the DLC System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Data Link Communications

2

Was the SIR Diagnostic System Check performed?

--

Go to Step 3

Go to SIR Diagnostic System Check in SIR

3

Inspect for proper connection of the scan tool to the data link connector at terminal 9.

Is the connection good?

--

Go to Step 4

Go to Step 14

4
  1. Disconnect the supplemental inflatable restraint sensing and diagnostic module.
  2. Inspect for proper connection to the supplemental inflatable restraint sensing and diagnostic module at terminal 5.

Is the connection good?

--

Go to Step 5

Go to Step 14

5
  1. Disconnect the SDM.
  2. Measure the resistance from DLC terminal 9 to ground.

Is the resistance greater than the specified value?

0.5 ohms

Go to Step 6

Go to Step 8

6

Connect a DMM between SDM terminal 5 and DLC terminal 9.

Is the resistance less than the specified value?

3 ohms

Go to Step 15

Go to Step 10

7
  1. Reconnect the SDM.
  2. Turn the ignition switch to the RUN position.
  3. Measure the voltage on the DLC from terminal 9 to terminal 4.

Is the voltage within the specified range?

0-5 V

Go to Step 9

Go to Step 11

8

Repair the short to ground in CKT 800.

Is the repair complete?

--

Go to SIR Diagnostic System Check in SIR

--

9
  1. Turn the ignition switch to the OFF position.
  2. Replace the supplemental inflatable restraint sensing and diagnostic module.

Is the repair complete?

--

Go to SIR Diagnostic System Check in SIR

--

10

Repair the open in CKT 800.

Is the repair complete?

--

Go to SIR Diagnostic System Check in SIR

--

11

Disconnect the VIU.

Is the voltage within the specified range?

0-5 V

Go to Step 12

Go to Step 13

12

Replace the VIU.

Is the repair complete?

--

Go to SIR Diagnostic System Check in SIR

--

13
  1. Turn the ignition switch to the OFF position.
  2. Repair the short to voltage in CKT 800.

Is the repair complete?

--

Go to SIR Diagnostic System Check in SIR

--

14

Repair the connection as needed.

Is the repair complete?

--

Go to SIR Diagnostic System Check in SIR

--

15
  1. Disconnect the VIU.
  2. Measure the continuity between terminal C474 of the VIU connector and terminal 9 of the DLC.

Is the resistance less than the specified value?

3 ohms

Go to Step 7

Go to Step 10