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Intermittent Powertrain Light on Gen3 V8

Demons1964

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The last week or so the powertrain light has been coming on every few days, and last Friday was remaining on for about 5 minutes, off for 1 minute, then back on and repeated like that for half an hour. Turned car off and back on and light still on. Today the light didn't come on at all during my 45 minute drive to work. Transmission still fine and normal readings on temp on gauge.

Questions:
1) Are fault codes still logged even though the check engine light isn't currently on?
2) Because it's intermittent is it likely to be a faulty oxygen sensor?

If there are any codes logged I'll get them scanned this arvo (Gen3 V8 so I can't read them myself) but I'm interested in anyone else's thoughts.
 

Murdoch

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O2 sensor i would imagine.
Could also be a small vacuum leak somewhere.
Any strange symptoms that you have noticed?
 

Mark

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odds are its either ur o2 sensor or ur pcv hose at the rear of ur intake, the last theory is ur oil pressure sender but if that was gone then it would be on perminently
 

Demons1964

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Thanks for that guys. I'm leaning towards oxygen sensors throwing a fault code due to a vacuum leak in the PCV hose. The last couple of weeks I've had a slight rev drop at idle when applying the brakes around about when the thermostat opens up (ie engine up at operating temperature). Strange thing is that it only happens once per day on the journey home from work, but hasn't coincided with the warning light coming on. The PCV hose is a bit soft and has a couple of tiny cracks near the throttle body, but no audible vacuum leak. If I do have oxygen sensor faults logged I'll replace the PCV hose as first course of action.

I won't be happy if it's the oil pressure sensor, only had it replaced 6 months ago and the warning light was on permanently for that when it failed, like Mark said.
 

minux

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Same light come son with transmission problems, be sure the auto has enough fluid and it isnt in need of a service.
 

BOGANV8

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I had the same problem with mine only came on every now and then

Had Holden check and Tech 2 said it was A fault code (RUNNING LEAN IN LEFT AND RIGHT BANKS) mechanic said it was the o2 sensors

Got home and spoke to a mate who use to rebuild Gen 3s (due to piston slap) and he said have a look at this pvc hose that runs from the throttle body to the back and then turns into a y piece and then goes to the rocker covers

Turns out the hose i have circled had a split in it the size of your finger and replaced that and then the back hose had the same thing had perished due to the oil replaced it with a plastic y from repco.....

Have posted some pics to show where the problem was hope it helps
 

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Demons1964

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You were spot on the money BOGANV8, your first pic told the story - the PCV hose split right near the throttle body. It's a bad design and without a 45 degree elbow there it's under a lot of stress. Anyway, came up with fault codes P0171 and P0174 (left and right bank running lean). It was an easy diagnosis though because the PCV hose split badly on the way to the mechanic last night: really bad idle and the air intake through the split was appropriately loud.

If anyone else wants a more permanent fix for the same problem my mechanic had the bright idea of a piece of high pressure fuel hose instead of the crappy Holden vacuum hose. I'll hazard a guess that backyard fix will last the life of the car. I'll just wait now for the rest of the standard PCV hose to start deteriorating.

Thanks to all for your help.
 

BOGANV8

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Good to hear i was useful and helped ya out :dance: :dance: :dance:

thats all i used was a bit of fuel hose so it should last the rest of its life of the car


Also check the one at the back too the one i have replaced with the Y section



Cheers Dave
 

sss1600

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Just had the same prob with my car today. Found the pcv angled hose split at the throttle body as mentioned already.
Replaced it with approx 5cm of 9.5mm ID Mackay fuel hose.
Revs dont drop to 500rpm now and engin check light hasnt come back on at low speeds yet. :)
 
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