P0140 = Aaaaaaand its back...

[Johnny Racer]

1999 OBS GMC Yukon SLT 5.7

Replaced both downstream O2 sensors the other day... Drove maybe 40 miles... And wouldn't ya know it... Damned check engine light came back on and sent me a P0140 = O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2.

Time to hunt for the fix.

Sensor brand new... hooked scanner up... graph shows activity spikes. Any ideas?

 

[SunlitComet]

re-seat the connector, clear the codes and see if it comes back. check the activity again.

 

[SunlitComet]

what brand of sensor btw?

 

[Johnny Racer]

Denso's. Are suggesting to re-seat the connector thinking it might be a "loose" connector? Ill give that a shot tomorrow after work. I was gonna swap the senors (both downstream) and see if it kicked a P0140 = O2 Sensor Circuit No Activity Detected Bank 2 Sensor 2 which would tell me the sensor is bad... easy fix. Replace defective sensor.

I had 5 or 6 miles since I cleared the code yesterday and when I came out of work, started truck, bam. Lights on.

 

[SunlitComet]

next time use only delco or delphi sensors please. yes loose connector.

 

[Johnny Racer]

Hmmmmmm... Wouldn't have suspected a Denso sensor being an unreliable part. If it were Bosch of something than yeah that would be my first thought. I'm gonna try that tonight. If that don't work, I'm gonna swap the tow downstreams and see if the code jumps banks. Then at least I'll rule out the sensor at that point.

Thanks for the info.

 

[Johnny Racer]

Swapped out the downstreams (Bank 1 to Bank 2 and Bank 2 to Bank 1)... Cleared code... Drove 5-6 miles... P0140 = O2 Sensor Circuit No Activity Detected Bank 1 Sensor 2. Same damned coded its been kicking so it didn't jump banks. That tells me the sensors are good. Gonna have to chase some wiring I guess now. Errrrrrrrrrrrrr. Emissions suck!

 

[SunlitComet]

run thru the test below to find a faulty signal wire possibly.

 

[Johnny Racer]

Thanks man... I had that very copy when I seen this post. Found the problem, broken wire towards the end of the harness. Fixed! Yay.

 

[Roxy]

1999 Yukon Denali 5.7 vortex. Automatic misfires and lugs with acceleration and shakes horribly according to tons and revs up and down...Just bought 3 months ago...had to put new Cats on so far and tune up was misfiring before all this and now more so with other symptoms I said so coming to conclusion it's probably the crankshaft sensor! No engine codes at this time as well...but misfire and cats a few months ago so we replaced cats 2 weeks ago but not 02 sensors...so Anyhoot Please give me your opinion and also that the location is behind the starter which needs to be pulled to remove and replace CSS and I also want to know if it will need to have timing checked after the fact..ok please let me know asap. I luv it and need it back to reliable...it had 200000 miles on it when purchased a few months ago but all else is a dream with her...ok thx much Roxy out