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.

[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??

[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 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.

[Rich84]

Any updates?