Vehicle is 2006 TrailBlazer LT, 4.2L I6, auto. trans.

Here is an interesting question for everyone, but especially Service Techs or Master Techs.

THERE ARE TWO PARTS FOR QUESTION #1. Please Consider Both PRIOR to Responding

Question 1 - First Part: For the 2006 Model Year TrailBlazer, is it possible to have an Ignition Switch Fail (i.e. have one or more contacts or internal parts be bad) and no Diagnostic Trouble Codes--DTCs--be stored in computer or PCM ??*

Question 1 - Second Part: The second part is that the following conditions are present:
1. The Battery is Known and Tests to be Good.

2. Some of the characteristic items, such as Instrument Cluster lights "acting crazy" or flashing rapidly/intermittently, interior lights flashing and other known anomalies, are NOT present.

3. Instrument Cluster acts normally, with the Trouble Check Sequence passing all items and the Indicator Lamps turning off when the Key is left in the Run position for more than 30 seconds--which is what you are supposed to do prior to starting the Trailvoy each time.

4. The Fuel Pump is on and running, when Key is in the Run position.

5. The starter cranks normally, with no dragging or slowing down, even after 10 plus seconds of cranking.

6. GM's "Hard Start", also termed as "Flooded Engine Start", Procedure as outlined in TB Owner's Manual does NOT work.

The only problem is TrailBlazer will NOT start.

Question 2: If the answer to Question 1 is "YES", then can you please explain exactly why the Output Voltage to either all or any of the 3 Ignition Switch Outputs can have output voltages below 10 Volts DC--usually 9 volts or less--and not cause any of the voltage dependent components/moduels/sensors lose some functionality, which normally results in generation of DTCs, yet NO DTCs are stored in the computer or PCM ??

 

The answer to question #1 is YES! All of the symptoms you note can be caused by a failing ignition switch.

Have a read through the article below:
Anatomy of the Ignition Switch

Try not to discount it due to its s-series roots. The s-series and GMT360/370 ignition switches are quite similar in design.

The reason for the voltage loss is due to increased resistance across the contacts in the ignition switch. The low voltage pass through causes the weird symptoms you have noted. If systems are not properly starting up to note their reduced power state, can they set a DTC?

 

1a.no way
1b.no crank signal.
1b.no fuel pressure.
1b.no spark.
1b.no injector pulse
1b.no gas
1b.something else

 

Huh? I have seen several GMT360/370 platform vehicles have a failed ignition switch without triggering codes. Just did my inlaw's TB last year. It would not turn over. No codes. Replaced ignition switch and all was well. In their case, it was the start side of the ignition switch which had the contacts fail. If the IGN sides fail, then I would agree, but there are a bunch of different contacts in there.