Envoy 2WD V6-4.3L VIN W (1998)
Body Control Module: Reading and Clearing Diagnostic Trouble Codes
Clearing Diagnostic Trouble Codes
You may NOT clear a DTC from the memory of the BCM by performing either of the following actions:
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Disconnecting the battery
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Disconnecting the BCM electrical connectors Perform one of the following steps in order to clear a DTC from the memory of the BCM:
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Use the scan tool.
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Perform 100 concurrent ignition cycles without the fault recurring.
You must clear the DTCs from the BCM after performing a repair. You may also clear the DTCs from the BCM in order to ensure that a malfunction
will not occur again. If the fault still exists, the DTC will reset after clearing the DTCs. If any current non-Passlock system related DTCs exist, diagnose
those DTCs before clearing the Passlock DTCs. When the Passlock DTCs are cleared, the BCM DTCs will also be cleared.
Reading Diagnostic Trouble Codes (DTCS)
WITH A SCAN TOOL
The BCM does not turn the SERVICE ENGINE SOON Malfunction Indicator Lamp (MIL) to the ON position. The BCM turns the SECURITY
malfunction indicator lamp (MIL) to the ON position for Passlock-related malfunctions. The recommended method for reading DTCs that are
stored in the memory is to use a scan tool plugged into the DTC connector. The DTC connector is located under the instrument panel on the left
side. Follow the scan tool instructions that are supplied by the tool manufacturer. The DTCs are stored in the memory of the Body Control Module
(BCM) as a current or a history DTC.
CURRENT CODES
The BCM sets the code as a current DTC when the following conditions exist:
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The BCM determines that the test conditions and failure conditions for a particular DTC are true.
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The current wake up cycle is still in effect.
All DTCs remain current until the following conditions exist:
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The next fault-free wake up cycle is performed.
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The BCM finds the test conditions are true.
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The BCM finds the failure conditions are false. The current code changes to a history code only when all of the above conditions are true.
HISTORY CODES
When a DTC reports a failure and the failure is not in the current wake up cycle, that DTC is stored as a history DTC code. The BCM performs
internal diagnostic tests in order to acknowledge that the related systems have reported a pass or fail condition. Each diagnostic test that fails is
recorded in the BCM memory. The BCM memory may be accessed with a scan tool in order to determine which DTC circuit is at fault.
Clear a history DTC by using one of the following methods:
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Complete 100 subsequent ignition cycles with no diagnostic test reporting a fail.
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Use the scan tool.
AFTER DIAGNOSIS IS COMPLETE
After you diagnose the problem and repair the discovered malfunction, clear any DTCs set and verify proper operation. In order to verify proper
operation, duplicate the conditions when the customer's complaint occurred. If a DTC was set, duplicate the test conditions for that DTC. The test
conditions are listed above the DTC table. Refer to Conditions for Setting the DTC. The DTC should not re-set after the repair has been made.
