Normal characteristic of MIL during Onboard diagnostic

[Bruce Nunnally]

File In Section: 06 - Engine/Propulsion System

Bulletin No.: 06-06-04-037

Service Bulletin Date: August, 2006

Subject: Normal Characteristics of Malfunction Indicator Lamp (MIL) During On-Board

Diagnostic (OBD) Inspection/Maintenance (I/M) Testing

Models: 2007 and Prior Passenger Cars and Trucks (Including Saturn)

2007 and Prior HUMMER H2, H3

2007 and Prior Saab 9-7X

The purpose of this bulletin is to inform dealers and

OBD inspection/maintenance testing facilities of normal

characteristics of the malfunction indicator lamp (MIL)

and the engine or powertrain control module (ECM

or PCM).

Some customers may comment on having been rejected

or having failed an OBD emission inspection. In some

cases, these vehicles do not need repair and may

have been rejected or may have failed the OBD

emission inspection due to a lack of understanding

with regard to the normal characteristics of the MIL and

ECM/PCM.

Following an engine run period, the MIL may not

illuminate on an ignition OFF to ignition ON transition

unless a 30 second delay is observed between key

OFF and key ON. The delay is necessary on some

control modules to allow the control module, either ECM

or PCM, to power down. Most vehicles may require

less time to achieve power down, but a 30 second delay

will satisfy all known applications. This is normal

operation for all GM control modules.

Some OBD I/M emissions test centers may not wait

30 seconds after a vehicle is turned off before

proceeding with the MIL bulb check, which could result

in a vehicle rejection or test failure.

To confirm proper MIL operation, wait 30 seconds

after the ignition is turned OFF before proceeding

with any key ON bulb check.

[JimD]

Thanks, Bruce. Never had occasion to use the 'save as text' function before today and did not know it was there.