Uplander 3.9 how many cats and 02 sensors?
July 24th, 2016, 6:41 PM
#1
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Uplander 3.9 how many cats and 02 sensors?
I just pulled some codes with a friend's cheap pocket scan unit and just trying to confirm there are only 1 catalytic converter and 2 oxygen sensors? I see only a single main cat and 2 oxygen sensors total, one off the rear exhaust manifold just before the converter and one sensor after the converter.
I've replaced the heated oxygen sensor that's before the cat but not the post converter 02 sensor since it typically reads converter condition.
Just making sure I haven't overlooked any other 02 sensors or precats hiding somewhere?
Thanks!
I've replaced the heated oxygen sensor that's before the cat but not the post converter 02 sensor since it typically reads converter condition.
Just making sure I haven't overlooked any other 02 sensors or precats hiding somewhere?
Thanks!
July 25th, 2016, 8:59 PM
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Hey guys well I'm new to GM engine management,etc (Nissans all my life) and haven't even bought a code scanner for it but a friend lent me his little Actron 9125 PocketScanner and it was a little confusing to be honest.
There is no CEL/MIL illuminated while the van is running, never has been.
However the scanner said this:
0 codes
4 ready: misfire, fuel, comp, catalyst.
No specific Pxxx or anything, I guess because it says '0 codes'. But the '4 ready...' I don't really get.
I replaced the upstream 02 with an AC delco unit about a year or two ago, new air filter, fresh oil change. Only things maintenance wise that could use replacing soon are the plugs/wires which have nearly 70,0000 miles on them.
I stay so busy and have no shop manual for this van that I'll probably just take it to a local shop I've dealt with in the past that are very trustworthy and fair. They have a Tech2 or whatever the dealer equivalent is.
I'm still thinking the loud coarse intake noise is coming from a TSB related variable intake manifold/tuning valve issue. Gas mileage has dropped from a consistent 18ish city to 14 city over the last few tanks. Full tanks hand calculated every time. Getting 290miles to full tank (to 'E') vs 350-380 prior to this.
There is no CEL/MIL illuminated while the van is running, never has been.
However the scanner said this:
0 codes
4 ready: misfire, fuel, comp, catalyst.
No specific Pxxx or anything, I guess because it says '0 codes'. But the '4 ready...' I don't really get.
I replaced the upstream 02 with an AC delco unit about a year or two ago, new air filter, fresh oil change. Only things maintenance wise that could use replacing soon are the plugs/wires which have nearly 70,0000 miles on them.
I stay so busy and have no shop manual for this van that I'll probably just take it to a local shop I've dealt with in the past that are very trustworthy and fair. They have a Tech2 or whatever the dealer equivalent is.
I'm still thinking the loud coarse intake noise is coming from a TSB related variable intake manifold/tuning valve issue. Gas mileage has dropped from a consistent 18ish city to 14 city over the last few tanks. Full tanks hand calculated every time. Getting 290miles to full tank (to 'E') vs 350-380 prior to this.
July 25th, 2016, 10:40 PM
#5
the scan is probably showing you the inspection/maintenance monitor status.
each major emission system runs a test to check system operation. when the test pass, the monitor indicates a pass status. when it runs and fails, dtc are set and the monitor shows a fail status. when codes are cleared, the monitor shows an incomplete status until the conditions are present for the monitor to run a test.
some examples of monitors are:
misfire monitors
02 sensor
evaporative emission
catalytic convertor
comprehensive component
each major emission system runs a test to check system operation. when the test pass, the monitor indicates a pass status. when it runs and fails, dtc are set and the monitor shows a fail status. when codes are cleared, the monitor shows an incomplete status until the conditions are present for the monitor to run a test.
some examples of monitors are:
misfire monitors
02 sensor
evaporative emission
catalytic convertor
comprehensive component
Last edited by tech2; July 25th, 2016 at 10:43 PM.
July 27th, 2016, 7:32 AM
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At 14mpg there's something definitely wrong. However I'm working 12hr days 5 days a week right now and have been too busy to drop the van off.
Based on the scanner and the tech 2's perfect explanation it simply seems that it's mechanical issue at this point and not a critical one.
I'm still leaning toward the variable intake not functioning properly but I'll report back once I can get it diagnosed. I can't afford too many more fillups at 14mpg. Or I'll at least have reason to trade for a used trailblazer ss v8 lol.
Based on the scanner and the tech 2's perfect explanation it simply seems that it's mechanical issue at this point and not a critical one.
I'm still leaning toward the variable intake not functioning properly but I'll report back once I can get it diagnosed. I can't afford too many more fillups at 14mpg. Or I'll at least have reason to trade for a used trailblazer ss v8 lol.
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July 27th, 2016, 7:08 PM
#8
when warmed up in closed loop operation; what are fuel trim readings at idle and 2500rpm.
the fuel trim reading will tell you a lot. Maybe the noise you hear is a vacuum leak letting false air into the system...this will skew the true maf reading....the 02 will read lean and the ecm will enrichen the fuel mixture based on bad sensor input.
what did the old 02 sensor look like when it was changed? pull one spark plug and see if its fuel fowled.
the fuel trim reading will tell you a lot. Maybe the noise you hear is a vacuum leak letting false air into the system...this will skew the true maf reading....the 02 will read lean and the ecm will enrichen the fuel mixture based on bad sensor input.
what did the old 02 sensor look like when it was changed? pull one spark plug and see if its fuel fowled.
July 28th, 2016, 8:18 PM
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Hey tech2 this little cheap actron doesn't display fuel trims I don't believe. I was actually going to order an actron 9680 because I haven't had time to drop the van off.
I replaced the 02 over a year ago simply because I had owned the van a couple of years and hadn't replaced it yet, though the van was running flawlessly.
I'll check the front bank plugs this weekend though, good idea.
With the uplander and other models you can't rev the engine above 4k rpm in park/neutral so it's hard to diagnose and physically pinpoint the noise without more advanced equipment or riding under the hood lol. Thanks for the feedback tech2!
I replaced the 02 over a year ago simply because I had owned the van a couple of years and hadn't replaced it yet, though the van was running flawlessly.
I'll check the front bank plugs this weekend though, good idea.
With the uplander and other models you can't rev the engine above 4k rpm in park/neutral so it's hard to diagnose and physically pinpoint the noise without more advanced equipment or riding under the hood lol. Thanks for the feedback tech2!