P1151 - 2000 Ex v8

[Kidd7]

I have 2000 Explorer EB v8 with about 200k miles. I'm getting a P1151 code; points to the upstream bank 2 O2 not switching (drivers side). I replaced both upstream O2 sensors within the past year. When data logging I can see this O2 stop switching, flatline; then the fuel trims for bank 2 max out.
Things I've done so far:
- cleaned the O2 sensor connector and filled with dielectric grease
- this worked for a while (few days/ week)
- There is an oil leak and gunk on the bottom of the truck (oil pan, trans area etc)
- I thoroughly clean up the gunk, again cleaning the O2 connector and sealing the wire side of the connector
- again this worked for a while
- Changed the O2 sensor
- The worked for much longer and I thought I has fixed it, but NO...
- Cleaned the MAF
- Changed plugs & wires b/c they needed done

Looking for some next steps. I'm thinking of taking some resistance measurements of the wires. There is no visible damage to the wires, although they are tight and run up the firewall so not easy to get to.

Some troubleshooting I've looked at point to thinks like MAF, vacuum leaks, fuel injectors, fuel pressure... These things are common to both banks (except the injectors) so I would think they would cause codes for both banks and not just one. Or at least affect how bank1 O2 is switching also, which I don't see that to be the case in the data.

 

[Hugheydee]

I have 2000 Explorer EB v8 with about 200k miles. I'm getting a P1151 code; points to the upstream bank 2 O2 not switching (drivers side). I replaced both upstream O2 sensors within the past year. When data logging I can see this O2 stop switching, flatline; then the fuel trims for bank 2 max out.
Things I've done so far:
- cleaned the O2 sensor connector and filled with dielectric grease
- this worked for a while (few days/ week)
- There is an oil leak and gunk on the bottom of the truck (oil pan, trans area etc)
- I thoroughly clean up the gunk, again cleaning the O2 connector and sealing the wire side of the connector
- again this worked for a while
- Changed the O2 sensor
- The worked for much longer and I thought I has fixed it, but NO...
- Cleaned the MAF
- Changed plugs & wires b/c they needed done

Looking for some next steps. I'm thinking of taking some resistance measurements of the wires. There is no visible damage to the wires, although they are tight and run up the firewall so not easy to get to.

Some troubleshooting I've looked at point to thinks like MAF, vacuum leaks, fuel injectors, fuel pressure... These things are common to both banks (except the injectors) so I would think they would cause codes for both banks and not just one. Or at least affect how bank1 O2 is switching also, which I don't see that to be the case in the data.

I'm having similar issues, but for bank 1 & 2.

I'm getting P1132, P1150, P1151, P0308, P0172, P0175. I've replaced plugs, both upstream sensors, and cleaned the MAF, IAC, And throttle body. Throttle body , iac, and exhaust tip were thoroughly coated in black soot. Cannot get it to run smooth, barely stays on with my foot on the gas.

 

[Turdle]

I'm having similar issues, but for bank 1 & 2.

I'm getting P1132, P1150, P1151, P0308, P0172, P0175. I've replaced plugs, both upstream sensors, and cleaned the MAF, IAC, And throttle body. Throttle body , iac, and exhaust tip were thoroughly coated in black soot. Cannot get it to run smooth, barely stays on with my foot on the gas.

First,
Check fuse 24 in the under hood fuse box.

Number 8 spark plug wire , or, injector for the 308 code. Possibly the wiring to injector


You might also try this

2nd gen issues? Try this first!

Sometimes a gremlin can be caused by the smallest thing. There are 2 large wire bundle connectors on the firewall. Both are held tight with a 10mm bolt. Any bad connection in either plug can cause just about any issue. from bad transmission shifting, bad o2 sensor readings, no start, no...

www.explorerforum.com

 

[Hugheydee]

First,
Check fuse 24 in the under hood fuse box.

Number 8 spark plug wire , or, injector for the 308 code. Possibly the wiring to injector


You might also try this

2nd gen issues? Try this first!

Sometimes a gremlin can be caused by the smallest thing. There are 2 large wire bundle connectors on the firewall. Both are held tight with a 10mm bolt. Any bad connection in either plug can cause just about any issue. from bad transmission shifting, bad o2 sensor readings, no start, no...

www.explorerforum.com

Which of these would be #24?

 

[Turdle]

Yellow 29a all by itself lower right

If you search you'll find a good example of 1997 Ford explorer fuse box . That's what I did to post first answer.

 

[Hugheydee]

Yellow 29a all by itself lower right

If you search you'll find a good example of 1997 Ford explorer fuse box . That's what I did to post first answer.

Fuse is good, checked the wires and can't find any shorts or any reason they wouldn't be working.

 

[Kidd7]

I cleaned / inspected the 2 main connectors in the engine bay then drove it and the O2 sensor was switching normal. Until we got home and pulled in the driveway, there was a little roughness and it seemed the o2 was switching slowly. I'll just keep monitoring the data from here.

 

[Kidd7]

Well she started flacking out again today. This is definitely an electrical issue as playing with the connections restores functionality for a time. I need to trace wires out now.

Anyone have the wiring diagram for bank2 O2 upstream wiring?

 

[Kidd7]

I’m working with this diagram for the wiring. In the O2 sensor which is the heater and which is the signal?

 

[Turdle]

Heater on left I believe.

Have you cleaned and reseated the square connector on firewall ?
Does the wiring to sensor ( the one under transmission) look good,? I've seen that drop and contact the front drive shaft. You might look that over

The connector pins in the plastic o2 sensor connector housing will sometimes push back, or, loosen. You can remove the female pins from truck harness and carefully reform them to click tightly back into place. Check the male pins are all fully inserted and lined up.

 

[Kidd7]

Cleaned and reseated both the square connector and the ECU connector inspected pins on both.
The O2 connector is mounted to the side of the tranny, from what I can see the wiring is good. I will look closer at the female pins.
Right now I’m measuring resistance from the O2 connector up to the ECU. It’s bouncing and was open when I first connected the multi meter. I am using paper clips so the connection isn’t the best.

 

[Kidd7]

Scratch all those previous measurements I was counting wrong. There connector counts backwards from the ECU, duh.

Both the heater & signal wires go up to the ECU with no resistance, even flexing the wires show no change. I don’t think this O2 wiring goes through the square connector, I could be wrong but it works its way up the firewall and into the ECU harness past the square connector.

All the pins and females looked good, not pushed back and clean.

Cleaned the connections again and added dielectric grease.

Pretty sure my rear main seal is leaking so I’m wondering if the connector has been contaminated with oil.

Other step would be a new ECU. These show up in the junk yard all the time so may be worth picking one up.

Question: are all v8 ECUs the same or is AWD or anything else specific? Any year differences?
Thanks for the help so far and hope this thread helps someone else.

Initial test drive was great; second time out we had problems again. Watching the data B2S1 will switch normally most of the time. Intermittently it will either stick at low or high for a while. When it sticks high the fuel trims max out on bank2 and she runs like trash.

 

[Turdle]

On the pcm you'll see a 4 digit code. That number needs to matched for replacement. Same year.

Sure does seem to be a connection issue.

Idea. Swap upstream sensors side to side. Not fun, but if the code moves to the passenger side that sure would be helpful.

 

[Hugheydee]

Fuse is good, checked the wires and can't find any shorts or any reason they wouldn't be working.

Fuel pump and fuel pressure regulator ended up being my issue

 

[Kidd7]

I agree it really does seem like a connection issue. I thought about swapping the 2 also, but am trying to avoid that ordeal. I did replace the O2 sensor in question just to rule that out. I'm going to look over the connector again today just to verify it's not loose.

I have access to battery powered O'scope; I'm thinking of putting together a pigtail so I can monitor the signal coming from the O2 sensor pretty much right at the sensor. I need to make some time to get to the bone yard though.

 

[410Fortune]

Inspect the pins inside the 02 connector make sure one of them did not back out from its lock

Dielectric grease does not conduct electricity get that stuff out of there

The connectors are weather tight as long as the seal is in there oil or water or salt should never get in if it does the damage should be obvious

So you have already put a different 02 in there and same issue? Just to clarify

So when I see code 1151 I don’t think problem with the 02 sensor… I think the 02 is doing its job. You may have a lean condition on bank 2
Bank 2 is drivers side just to make sure

This code means the 02 sensor is pre heating normally but then once in closed loop it’s reading a lean condition. The pcm tries to correct it by adding fuel and is not able to add enough to correct the lean condition and then you get a code.

Lean on bank 2 could be low fuel
Pressure, a weak /bad injector, or air
Leaks at the exhaust manifold or?

I understand with live data the 02 sensor quits switching and wiggling the wires corrected it? Is that still true?

Something to think about

 

[Kidd7]

So you have already put a different 02 in there and same issue? Just to clarify

Correct installed a new one. Both performed the same, so not a sensor issue. Did that just to rule it out. Never thought that was the issue.

Bank 2 is drivers side just to make sure

Correct, drivers side it what I'm looking at. Thankfully the easier one to get to.

Lean on bank 2 could be low fuel
Pressure, a weak /bad injector, or air
Leaks at the exhaust manifold or?

I understand with live data the 02 sensor quits switching and wiggling the wires corrected it? Is that still true?

New fuel pump recently, low fuel pressure should affect both sides, correct?
Wouldn't an air leak cause both sides to be lean? or possible an air leak on bank 2 only? intermittently? what could cause that? This would be quite a large leak.
NO exhaust leaks

Wiggling: No, have not seen any difference with moving the wires. Resistance was solid at ~.02 ohms no matter how much I moved the wires. Logging live data shows switching, then not switching, then switching again all while driving, no intervention.

Sometimes the O2 signal goes low and for the most part the truck drives ok, sometimes it goes high, then the truck runs bad b/c the fuel trims go to max at that point.
Very intermittent also, it never seems to happen cold, but does not consistently happen hot either.
I had the timing cover, water pump, timing chain set replaced, but this started happening before that. That included fresh oil, coolant, etc. This was due to a coolant leak thought the timing cover gasket.

 

[410Fortune]

Very interesting! It must be in the wiring to that 02 sensor maybe on the power side of things? The 02 sensors get 4 wires a power and ground for the pre heater and then a signal wire to the pcm and the ground wire for the signal

I would check all 4 wires
So you have a 99 wiring book?

 

[Kidd7]

I unfortunately only have a Haynes manual to go by.

The O2 sensor has 2 white wires, a grey & a black. Any insight into which wires are which and a resistance measurement that is "good?"

I don't think its the O2 side of wiring, same symptoms with 2 different new O2's.

 

[410Fortune]

Haynes manual is not helpful

Here is the book you need

2000 Ford Explorer Mercury Mountaineer Electrical Wiring Diagrams Manual | eBay

Includes cross-referenced electrical schematic and full-view illustration wiring diagrams. Original OEM Ford Factory Electrical Wiring Diagrams Manual. Not a reproduction. Our manuals are complete and fully usable with no missing sections.

www.ebay.com

The issue is likely on the truck side of the wiring so this book will locate all wires and their connectors and locations in the truck