Dreaded 02 codes with Longtubes
Thread Starter
Heel & Toe
Joined: Oct 2023
Posts: 15
Likes: 3
From: NE GA
Dreaded 02 codes with Longtubes
Hello everyone, as you can tell I am a new member here! I have recently transitioned from a SLP ZL575 to a H/C C5Z. The seller did not disclose the CEL issues and I was lucky enough to get 5 miles from his house prior to them popping on.
I am getting the normal P0154/P0134 codes. The car has LG Pro longtubes. This weekend, I replaced the front 02 sensors with new Denso (rear) 02 sensors and corrected the 02 routing. The PO had run the front 02 to opposite side harnesses.
Immediately, the car seemed to idle slightly better and returned better fuel mileage. It also appears to be running a bit richer. I am noting this by the clearly more present rich smell. This initially led me to believe I had fixed the issue. However, it has returned. The most odd part to me is that it sometimes take 30-40 miles for the codes to appear. I am at a loss from here. Where to next? Potentially tune parameters being too “tight?”
Thank you in advance for any assistance.
I am getting the normal P0154/P0134 codes. The car has LG Pro longtubes. This weekend, I replaced the front 02 sensors with new Denso (rear) 02 sensors and corrected the 02 routing. The PO had run the front 02 to opposite side harnesses.
Immediately, the car seemed to idle slightly better and returned better fuel mileage. It also appears to be running a bit richer. I am noting this by the clearly more present rich smell. This initially led me to believe I had fixed the issue. However, it has returned. The most odd part to me is that it sometimes take 30-40 miles for the codes to appear. I am at a loss from here. Where to next? Potentially tune parameters being too “tight?”
Thank you in advance for any assistance.
Thread Starter
Heel & Toe
Joined: Oct 2023
Posts: 15
Likes: 3
From: NE GA
Oktx,
I know the car was tuned, but I do believe the car had a cam and supporting mods installed and tuned at the same time, with the headers being added later. Could it be a parameter thing? The car runs amazing, but I can stand a pesky dash light.
I know the car was tuned, but I do believe the car had a cam and supporting mods installed and tuned at the same time, with the headers being added later. Could it be a parameter thing? The car runs amazing, but I can stand a pesky dash light.
Pro
Joined: Jul 2020
Posts: 548
Likes: 132
From: Texas
I would think the car would need tuned for the headers.
Thread Starter
Heel & Toe
Joined: Oct 2023
Posts: 15
Likes: 3
From: NE GA
I don’t totally disagree, but I do know it does have a tune. Per the PO, it was tuned prior to the LTs being installed. However, there are countless members that add LTs and don’t get their car tuned. Is it possible the present tune has that sensitive of parameters?
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
I would trace the wiring. Those codes are showing no O2 activity so any data from the sensors aren't reaching the ECM. Also check for any vacuum or exhaust leaks. I would also put the original O2's back in with the correct side wiring, them move on from there. When you changed the O2 sensors and the wiring you made two changes as once so diagnosis becomes harder and you don't know if you eliminated an issue or fixed one and created a second.
Team Owner
Joined: Oct 1999
Posts: 31,976
Likes: 487
From: Guinness Its whats for B'fast JAWGA
CI 3-4-5-9 Veteran
I would trace the wiring. Those codes are showing no O2 activity so any data from the sensors aren't reaching the ECM. Also check for any vacuum or exhaust leaks. I would also put the original O2's back in with the correct side wiring, them move on from there. When you changed the O2 sensors and the wiring you made two changes as once so diagnosis becomes harder and you don't know if you eliminated an issue or fixed one and created a second.
LG also recommends running rear O2s on the front using an adapter harness. Trace it to see if any wires were burned, connections melted, BTDT. I've used p clamps using the tunnel shield bolts to route wires.
Thread Starter
Heel & Toe
Joined: Oct 2023
Posts: 15
Likes: 3
From: NE GA
I should clarify - when I swapped 02s this past weekend, I corrected the PO’s routing as he had the sides swapped.
I am still getting the same codes as prior, being P0134 and P0154. I have dropped the car off at MTI racing in hopes they can track down the issue. I will update the thread as I receive updates.
To my eye and limited knowledge, all wiring looked fine.
I am still getting the same codes as prior, being P0134 and P0154. I have dropped the car off at MTI racing in hopes they can track down the issue. I will update the thread as I receive updates.
To my eye and limited knowledge, all wiring looked fine.
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Race Director
Joined: Apr 2007
Posts: 11,150
Likes: 890
From: South Western Ontario
You have the rear O2's plugged into the front O2 spots with adapter harnesses, right?
FYI, using front or rear sensors doesn't make a difference functionally. But some of the headers put the primary sensors so far away that the wires on the front sensors won't reach the plugs hence the recommendation to use rest sensors with adapter harnesses.
FYI, using front or rear sensors doesn't make a difference functionally. But some of the headers put the primary sensors so far away that the wires on the front sensors won't reach the plugs hence the recommendation to use rest sensors with adapter harnesses.
Team Owner
Joined: Oct 1999
Posts: 31,976
Likes: 487
From: Guinness Its whats for B'fast JAWGA
CI 3-4-5-9 Veteran
You have the rear O2's plugged into the front O2 spots with adapter harnesses, right?
FYI, using front or rear sensors doesn't make a difference functionally. But some of the headers put the primary sensors so far away that the wires on the front sensors won't reach the plugs hence the recommendation to use rest sensors with adapter harnesses.
FYI, using front or rear sensors doesn't make a difference functionally. But some of the headers put the primary sensors so far away that the wires on the front sensors won't reach the plugs hence the recommendation to use rest sensors with adapter harnesses.
Safety Car
Joined: Jan 2012
Posts: 3,956
Likes: 520
From: Da U.P.
Drifting
Joined: Mar 2018
Posts: 1,365
Likes: 414
From: New Jersey
Check that the fuses for the 02 heater circuit. They may be blown. That could cause your problem. Also you should be able to turn the key on with the engine not running as feel if the warm up. A cheap obd2 scanner will help immensely with trouble shooting this. As you will be able to determine what's going on with them.
Thread Starter
Heel & Toe
Joined: Oct 2023
Posts: 15
Likes: 3
From: NE GA
What is traditionally a cause for the fuse to blow? I have seen several forums referring to blown fuses continually blowing.
I believe my codes are purely from slow response from the front 02s. I have adapters in the car to run the rear 02s up front. The car runs great and pulls hard, I just can’t stand a CEL.
I believe my codes are purely from slow response from the front 02s. I have adapters in the car to run the rear 02s up front. The car runs great and pulls hard, I just can’t stand a CEL.
Safety Car
Joined: Jan 2012
Posts: 3,956
Likes: 520
From: Da U.P.
What is traditionally a cause for the fuse to blow? I have seen several forums referring to blown fuses continually blowing.
I believe my codes are purely from slow response from the front 02s. I have adapters in the car to run the rear 02s up front. The car runs great and pulls hard, I just can’t stand a CEL.
I believe my codes are purely from slow response from the front 02s. I have adapters in the car to run the rear 02s up front. The car runs great and pulls hard, I just can’t stand a CEL.
Thread Starter
Heel & Toe
Joined: Oct 2023
Posts: 15
Likes: 3
From: NE GA
Interesting… I am in limbo while the car is at MTI. I will likely suggest they replace the current 02s in the front bungs with OE fronts. Bummer as I just replaced them, but I’d rather not see the pesky light on. I will update the forum as MTI Racing provides me updates on the car.