GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The Passlock™ sensor monitors CKT 1870 at terminal C and terminal D while transmitting messages in order to determine if the message was sent. The Passlock™ sensor will resend messages when preempted by more important messages.

Conditions for Setting the DTC

The Passlock™ sensor monitors CKT 1807 at terminal C and terminal D while transmitting messages in order to determine whether the message was sent. If the Passlock™ sensor attempts to send a message and does not detect the message of CKT 1807, the message will be resent. After 3 attempts to send a message (in the absence of a more important message and not detecting the message), DTC U1193 is set.

Conditions for Clearing the MIL/DTC

    • A history DTC will clear after 100 consecutive ignition cycles occur without a fault.
    • Use the Tech 2 scan tool in order to clear history and current DTCs.

Diagnostic Aids

    • A short to ground or a short to battery may set the DTC. The identified malfunctions would prevent serial data communications and the DTC may not be retrieved as a current DTC.
    • Faulty electrical connections or wiring cause most intermittent faults. Occasionally, a damaged Passlock™ sensor is at fault. Refer to Intermittents and Poor Connections Diagnosis for a detailed explanation of how to locate and repair intermittent conditions.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step confirms the presence of a malfunction.

  2. This step tests for a DTC that may cause DTC U1193 to set.

Step

Action

Value(s)

Yes

No

1

Did you perform the Data Link Communications System Check?

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Go to Sep 2

Go to Diagnostic System Check - Data Link Communications

2

  1. Turn the ignition switch to the OFF position.
  2. Wait 10 seconds.
  3. Turn the igntion switch to the RUN position.
  4. Wait 75 seconds.

Is the DTC U1193 current?

--

Go to Sep 3

Go to Sep 4

3

  1. Turn the ignition switch to the OFF position.
  2. Replace the Passlock™ sensor.

Is the repair complete?

--

Go to Diagnostic System Check - Data Link Communications

--

4

Are any other Passlock™ sensor DTCs current?

--

Go to Diagnostic System Check - Body Control System in Body Control System

Go to Sep 5

5

  1. Clear the DTCs.
  2. Turn the igniton switch to the OFF position.

Is the procedure complete?

--

Go to Diagnostic System Check - Data Link Communications

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