ARRRRRRGH! More fault codes- Help!

[Steve Cole]

So I have these annoying fault codes that keep popping up P0053 and P0059- (Heater resistance bank 1 sensor 1 and bank 2 sensor 1)

It's a 2005 5.3 truck engine with a stand alone harness from BP-Automotive. He also deleted the rear oxygen sensors when he re-flashed my ECU. Two brand new AC Delco O2 sensors in the front positions. I just had the exhaust done and I have about 50 miles on the truck since the swap. I have actually had these fault codes before the exhaust was done, pretty much as soon as I got the motor running. I thought once the exhaust was installed these codes would go away but nope.

This has to be something simple for both sensors to be faulting, but I don't know what it could be.
I am pretty sure I can rule out faulty sensors, damaged connectors, blown fuses, fuel pressure, exhaust leaks, and it seems like I could hear a vacuum leak on the engine. I can't rule out wiring because I have already found a mistake with the harness. Not to get off topic but, two of the harness wires that go to the drivers side coil packs were switched (backwards) and the left side of the engine was not firing so I was only running on 4 cylinders. I de-pinned those wires and swapped them around so that's fixed now. Anyway, back to the problem, Does anyone have a suggestion what I can check? I need to get a wiring diagram so I can verify the harness wires aren't switch around like the coil wires were but after that, not sure what to look at next. The fact that both sides are faulting makes me think it is something simple.

Here is a description of the fault:

P0053 code definition
HO2S Heater Resistance (Bank 1 Sensor 1)

What the P0053 code means
This code means the Heated Oxygen Sensor (HO2S) Resistance is out of range on engine bank 1 (side of engine with cylinder #1) and the sensor upstream or in front of the catalytic converter.

What causes the P0053 code?
Faulty HO2 sensor
Damaged or disconnected electrical connector at the oxygen sensor
Faulty or shorted wiring in the oxygen sensor circuit
Blown fuse for the HO2S sensor
Low or excessive fuel pressure
Vacuum leak on the engine
Excessive exhaust leaks
Faulty ECU (Engine Control Unit), in rare cases

[ls1nova71]

I think you're right, it's unlikely that both sensors are bad at the same time, and if everything else has checked out, it would seem to me it would come down to a wiring issue. Before we go there, Have you double checked all the harness grounds? Remove them, clean them up so they are clean and bare metal, then bolt them back on and make sure they are tight. If that has been done, check the fuse again, and specifically the terminals where the fuse plugs in. Just testing the top of the fuse doesn't always work, because you could have a good connection on the power side, and through the fuse, but maybe not from the fuse to the other terminal.

The power wire is really the only place the heater portions of both sensors are connected, which is what makes me think the problem is on that circuit. You could also check for power at the O2 plugs to make sure you actually have power there, it will be the 2 pink wires.

[Wgesnerjr]

I had a stumbling problem on start up that went away within the first 45 sec of a cold start. I started to think the heater on my O2 sensors may have died so I made a test harness like described here: https://www.motor.com/magazine-summa...cuit-failures/ Used a simple side marker light from an old harness and a plug from an O2 sensor from Pull a Part.

Turned out that the muffler shop must have left the O2 sensor in the pipe when welding my new exhaust. Seems the heat or the arc fried the sensors. Replaced with new Delco ones and have been great ever since.

You can read up on my saga here:https://67-72chevytrucks.com/vboard/...=774609&page=3

Page 3 Post #58 is where I started the testing the heater circuit on the O2 sensors.

[AussieinNC]

Assuming you had ECM reflashed to suit new build....

Perhaps they made an error and frgot to power on front sensors....check for power on the input wires where tey plug onto the sensor lead...

Swap out one sensor with a known good one...reset codes....check for new ones...if no new one for the newly installed sensor replace the other one...

[Steve Cole]

Originally Posted by ls1nova71

I think you're right, it's unlikely that both sensors are bad at the same time, and if everything else has checked out, it would seem to me it would come down to a wiring issue. Before we go there, Have you double checked all the harness grounds? Remove them, clean them up so they are clean and bare metal, then bolt them back on and make sure they are tight. If that has been done, check the fuse again, and specifically the terminals where the fuse plugs in. Just testing the top of the fuse doesn't always work, because you could have a good connection on the power side, and through the fuse, but maybe not from the fuse to the other terminal.

The power wire is really the only place the heater portions of both sensors are connected, which is what makes me think the problem is on that circuit. You could also check for power at the O2 plugs to make sure you actually have power there, it will be the 2 pink wires.

Thanks for the reply Eric,
I replaced the fuse, Installed a different sensor that I removed from the donor truck, checked for power at the plug, and verified my single harness ground. All checked good but it is still throwing those fault codes. What else can I check??

[Steve Cole]

Originally Posted by AussieinNC

Assuming you had ECM reflashed to suit new build....

Perhaps they made an error and frgot to power on front sensors....check for power on the input wires where tey plug onto the sensor lead...

Swap out one sensor with a known good one...reset codes....check for new ones...if no new one for the newly installed sensor replace the other one...

Aussie,
I did all that, no bueno.

[Steve Cole]

The saga continues: So I cleared the codes two days ago and went for a drive. My check engine light came back on very quickly and I assumed it was the same codes but no, instead of the O2 sensors I now have PO171 and PO174 (fuel trim system lean bank 1 and bank 2).

Possible causes:

HO2S element is contaminated, deteriorated, or has failed.
Vacuum hose is disconnected, broken, leaking, or loose.
One or more injectors restricted or pressure regulator has failed.
Low fuel pressure (fuel filter clogged, pressure regulator failure)
Fuel control sensor is out of calibration (ECT, IAT, or MAF)
Air leaks in intake manifold, exhaust pipes, or exhaust manifold.

I am certain the my O2 sensor faults are probably coming back the next time I drive it so I suspect these new fault codes are somehow related.

Let me address some of the possible causes-

O2 sensors were originally brand new AC Delco units but I recently replaced with the two that came off the donor truck (for troubleshooting)
Vacuum hoses all look good. The vacuum hose that connects to the brake booster was a little loose though so I tightened yesterday.
I had my injectors cleaned and flow checked not too long ago
Fuel filter and pressure regulator are new (less than 100 miles on everything)
Fuel control sensor out of calibration- Could be, I don’t know
Air leak in intake/exhaust manifolds or exhaust pipes- I checked the intake and exhaust manifolds yesterday, all is torqued. I checked the exhaust pipes from the headers to half way back yesterday. So far, the clamps are tight and welds complete. Will do the back half today.

All these faults have to be related somehow; I am looking for suggestions to troubleshoot this.

Anyone??

[Steve Cole]

So I cleared the codes again and took it on a short 5 mile drive. This time the PO174 code came back but the PO171 did not. I probably didn't drive it long enough though. Anyone have any ideas??

[ls1nova71]

Have you checked the fuel pressure? Just wondering if maybe you have a bad filter/regulator. I've seen bad ones right out of the box on auto part store house brand filters.

[Steve Cole]

Originally Posted by ls1nova71

Have you checked the fuel pressure? Just wondering if maybe you have a bad filter/regulator. I've seen bad ones right out of the box on auto part store house brand filters.

I have not checked the fuel pressure Eric but I just ordered a test gauge so I will check it next week. Thanks for your suggestion!

[akdg87]

are the o2 sensor harness routed to the correct sides? IE bank one is truly on bank 1.

[ls1nova71]

Originally Posted by akdg87

are the o2 sensor harness routed to the correct sides? IE bank one is truly on bank 1.

Good call, I hadn't thought of that. Have seen it happen in the past, but can't remember the exact issue it causes. Definitely worth looking into.

[Steve Cole]

Originally Posted by akdg87

are the o2 sensor harness routed to the correct sides? IE bank one is truly on bank 1.

I will double check this today, along with checking the fuel pressure.

Thanks for the suggestion!

[edgeleycanuck]

I have just recently had my truck wired and fired by a local performance shop. I have only started it maybe 10 times and driven a couple of miles. It is a used 4.8 out of a 2000 pickup. On initial startup it has been running very rich especially when cold, it now is not starting with out some throttle, I have not checked for codes yet, the wiring harness is new as are the oxygen sensors. The mechanic asked me if the intake gaskets have been changed, I bought the engine in a wrecked donor vehicle so I don't know. Long story short he said the truck intake manifolds are known to fail( not sure of which model years), he said the engine draws more air and wants to add fuel.... Anyway I have no idea if my blathering is helpful but just wondering if the possibility of a vacuum leak you mention could be an intake gasket failure?

[Steve Cole]

Originally Posted by Steve Cole

I will double check this today, along with checking the fuel pressure.

Thanks for the suggestion!

I verified that bank 1 connector is on the drivers side as it should be.
I also checked my fuel pressure. When the key is turned to the first position, the fuel pressure goes to 60 for a couple of seconds then drops to 50. When running, it stays steady at 60 psi.

edgeleycanuck:

Thanks for the suggestion, I am willing to try anything at this point. Before I installed the engine, I replaced the intake manifold gasket and tightened/torqued it using the correct tightening/torqueing sequence so I don't think this is the culprit.

Can someone identify all the vacuum hoses I should check?

My configuration is not stock. I am using a LS6 valley cover with a hose running from it to a oil catch can and from the can to the top of the intake manifold. I have the port on the rear of the drivers side valve cover capped off and the port on the front of the passenger side valve cover running to the throttle body. My brake booster hose is too big but I have it cinched down with a hose clamp pretty good until I can come up with a permanent solution

[tbrown5079]

At this point I would find someone with a smoke machine to determine where all the vacuum leaks are and repair them before you replace anything else. I fought the PO171 and PO174 codes until I finally borrowed a smoke machine and found a gasket out of place on the right bank valve cover (the side the donor vehicle was hit on. The stud on the valve cover was even bent). I know this can be very frustrating. Tbrown

[Steve Cole]

Originally Posted by tbrown5079

At this point I would find someone with a smoke machine to determine where all the vacuum leaks are and repair them before you replace anything else. I fought the PO171 and PO174 codes until I finally borrowed a smoke machine and found a gasket out of place on the right bank valve cover (the side the donor vehicle was hit on. The stud on the valve cover was even bent). I know this can be very frustrating. Tbrown

Hey Tbrown, thanks for the suggestion but I seriously do not think it is a vacuum leak. I put a code reader on it with "live data" enabled and watched my fuel trims. When you come off idle and go to about 2000 rpm, the short term fuel trims should get better if your problem is a vacuum leak. My numbers did not change at all. At this point I am thinking it is tied to the other fault codes I am getting (P0053/P0059) O2 heater resistance banks 1&2 sensor 1.

Still looking for ideas!!

[Rich84]

Any updates?