P1151 on Replacement Engine


backporch

Member
Joined
Dec 31, 2017
Messages
104
Reaction score
0
Points
16
Location
NJ
Vehicle Year
1999
Make / Model
Ranger Off Road
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Tire Size
245 75R16
I could use some help with getting over the next hurdle addressing a p1151 check engine light. I have a few weeks to address this and any other CEL issues prior to state inspection.

So far i have only taken 3 short trips with the Ranger since putting the engine in.

I think that 1151 is an issue with a reading from the driver's side catalytic converter reading a less than optimum air/fuel reading.

The motor runs well. I tried my best to address any any vacuum leaks from the front axle which now has manual hub locks. The upper intake manifold is new.

I have access to some simple tools like an infrared non contact thermometer and the torque app to read O2 sensor readings.

If anyone can suggest some diagnostics or most common points of failure, that would be invaluable.
 


Rock Auto 5% Discount Code: 57CD9601BD5AB4 Expires: July 1, 2019

Dirtman

Well-known member
EMT / Paramedic
Joined
May 28, 2018
Messages
1,079
Reaction score
112
Points
63
Location
Over there --->
Vehicle Year
2009
Make / Model
Ford
Engine Type
2.3 (4 Cylinder)
Engine Size
2.3
Transmission
Automatic
2WD / 4WD
2WD
Tire Size
So friggin big!
My credo
give me money.
What was the engine state before the swap? Any previous CELs? Was this a completely direct swap? Meaning exact same engine and sensors? Was the exhaust or more importantly the o2 sensors changed with the swap? If you have a scanner that has torque, it should say if the heater for the o2 is coming on, and you should be able to see live data to see if its switching. Lot of variables.

My guess, you replaced an engine with a bad sensor that you didnt replace with the engine. Or you have a vacuum leak, or broke a connection. Need more info. But wait about 4 minutes and the geniuses here will chime in with better info...
 

Denisefwd93

Active member
Joined
May 20, 2015
Messages
1,967
Reaction score
8
Points
38
Location
South East PA
Vehicle Year
1993
Make / Model
Ford
Engine Size
4.0
Transmission
Automatic
make sure the wiring harness for the O2 sensors is not pinched between the bellhousing and the engine, don't ask me how I know! [emoji1787]. It's almost like they designed it to drop right between there when they're apart!

As I understand it with these O2 sensors, it's not the sensor goes bad but the heater in them, that goes bad and they don't reach the required temperature.
 
Last edited:

backporch

Member
Joined
Dec 31, 2017
Messages
104
Reaction score
0
Points
16
Location
NJ
Vehicle Year
1999
Make / Model
Ranger Off Road
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Tire Size
245 75R16
Thanks for the responses. There are geniuses here.

The motor was from an explorer... with <90K miles. Was not running when I got it but was rumored to run fine before the freeze plugs rusted through and it lost coolant. I took the Explorer engine and from the Ranger ( had california emissions and no EGR) swapped the exhaust headers with new gaskets, replaced most of the exhaust studs, replaced the upper intake gasket with new and used the no-EGR ranger Intake.

I think the previous owner replaced both forward O2 sensors and coil pack. Not sure what issue he was chasing, but the Ranger motor had cracks in both heads and was not running.

I tried to check the wire for the O2 sensor on the driver's side. I don't think it is caught in the block. The O2 sensor lead was coiled up and zip tied. I guess there is a chance the connector is not all the way clicked in or damaged. I was thinking the Torque readings would help identify a broken or disconnected O2 sensor
 

RonD

Well-known member
Joined
Jun 2, 2012
Messages
12,790
Reaction score
157
Points
63
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
You should always look up OBD codes on a full list, like here: https://therangerstation.com/tech_library/OBD-II_codes.shtml

That way you can see the OTHER codes the computer choose NOT to use.

P1151 Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2

Upstream O2 on Bank 2, so drivers side, indicates LEAN
So not a Cat issue

Doesn't say its not switch/working, says that its showing Lean, and that means computer has added at least 20% more fuel to drivers side and O2 still showing lean

Generally computer will run + or - 10% fuel trims without setting a code, at 15% it will set a pending code usually and at or above 20% it will set code and turn on CEL
But each model and engine has different software for that

P1xxx codes are manufacturer specific, since Ford made the computer then P1151 would be a Ford specific code, seen on above list

P0xxx are generic OBD codes, applies to all makers, models and engines

You should have gotten P0174 lean on bank 2, first, its odd you didn't

Could be O2 sensor issue since its only on one bank
Could be steady misfire on bank 2, injector or spark issue
Could be exhaust manifold leak on bank 2
Could be lower intake vacuum leak on bank 2

These would effect Both banks so:
Can't be upper manifold vacuum leak
Can't be MAF sensor issue
Can't be fuel pressure issue
Can't be PCV Valve issue
 

backporch

Member
Joined
Dec 31, 2017
Messages
104
Reaction score
0
Points
16
Location
NJ
Vehicle Year
1999
Make / Model
Ranger Off Road
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Tire Size
245 75R16
That was the only code. No other code or pending codes.

I would like to start ruling out other possible causes

Would there be a 0v reading for an O2 sensor with a bad wire or connection?

Would a misfire typically trigger another engine code?
 

Denisefwd93

Active member
Joined
May 20, 2015
Messages
1,967
Reaction score
8
Points
38
Location
South East PA
Vehicle Year
1993
Make / Model
Ford
Engine Size
4.0
Transmission
Automatic
just replace the oxygen sensor? Yes I know, we all painfully know how expensive they are.
 

RonD

Well-known member
Joined
Jun 2, 2012
Messages
12,790
Reaction score
157
Points
63
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
O2 sensors have 4 wires, yes, unplug connector, look for corrosion, or frayed wires and plug it back in, clear codes and drive

O2 sensors have a heater circuit, 2 wires, which is monitored by computer
P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)


The O2 sensor part, the other 2 wires, generates its own voltage when heated up above 600degF
Computer, of course, monitors that warm up and watch for it to start generating volatge
If it doesn't
P0154 02 Sensor Circuit No Activity Detected (Bank 2 Sensor 1)

With no other codes besides P1151 it would be odd for the O2 sensor to be the problem, but................

No P0174 System too Lean (Bank 2) is also odd

You could try a new O2 or swap O2s around
 

backporch

Member
Joined
Dec 31, 2017
Messages
104
Reaction score
0
Points
16
Location
NJ
Vehicle Year
1999
Make / Model
Ranger Off Road
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Tire Size
245 75R16
I may try to break free the oxygen sensors and swap them. Replacment sensors don't look too bad. I checked on RockAuto and they appear to run 25-50 dollars each. Of course, $10 is too much to replace a part that isn't bad.

I am not looking forward to physically breaking them loose. I do have an 02 socket/wrench and some breaker bars. Is the best way to go in from the top or through the wheel well?

Anyone know if it is OK to use a penetrant for the swap? I have only broken sensors behind the cat loose and I did use some penetrant there. usually replaced them at that point.

Also... I noticed RockAuto has two different part numbers for left and right. Could they not be swappable?
 
Last edited:

Denisefwd93

Active member
Joined
May 20, 2015
Messages
1,967
Reaction score
8
Points
38
Location
South East PA
Vehicle Year
1993
Make / Model
Ford
Engine Size
4.0
Transmission
Automatic
I'm pretty much under the assumption the only oxygen sensors that come out easy are the ones that are installed on new cars still on the lot. all others I hope you have the heavy artillery because my other assumption is they cannot be taken out and reused!
 

adsm08

Well-known member
Supporting Member
Ford Technician
TRS 20th Anniversary
Joined
Sep 20, 2009
Messages
30,772
Reaction score
558
Points
113
Location
Dillsburg PA
Vehicle Year
1987
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Tire Size
31X10.50X15
I may try to break free the oxygen sensors and swap them. Replacment sensors don't look too bad. I checked on RockAuto and they appear to run 25-50 dollars each. Of course, $10 is too much to replace a part that isn't bad.

I am not looking forward to physically breaking them loose. I do have an 02 socket/wrench and some breaker bars. Is the best way to go in from the top or through the wheel well?

Anyone know if it is OK to use a penetrant for the swap? I have only broken sensors behind the cat loose and I did use some penetrant there. usually replaced them at that point.

Also... I noticed RockAuto has two different part numbers for left and right. Could they not be swappable?

I prefer to get at them from under. It usually puts them right in your face. I will get my socket location figured out, run the engine for a bit, bust them loose and then let things cool for a bit.

You can use penetrating oil but I prefer heat.


The different part numbers is because the pigtail lengths are different. They do it so you can't plug them in on the wrong side.
 

RonD

Well-known member
Joined
Jun 2, 2012
Messages
12,790
Reaction score
157
Points
63
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
Crowfoot wrench can work well on O2 sensors

7/8 or 22mm is the normal size, 7/8 is 22.2mm so either will work fine

The flare nut 6 point crowfoot is better for O2s, doesn't slip off
 
Last edited:

mazdab40004x4

New member
Joined
Dec 9, 2010
Messages
96
Reaction score
1
Points
0
Location
Atlanta, GA
Vehicle Year
1994
Make / Model
Mazda
Engine Size
4.0 V6
Transmission
Automatic
It's possible I got lucky, but I just removed and replaced both my O2 sensors this weekend with no problem. Did it from under the truck. I only have two upstream L/R (pre-OBDII). The one on the right had just enough room for the O2socket but not a ratchet so I slipped a wrench over the end of the socket (the socket has a 7/8 6-point on the end) and it came right out. The left I was able to get the ratchet on and it popped off too. No bashing of knuckles or anything. The new ones had antisieze already on them out of the box so hopefully the next time will be just as easy.
 

backporch

Member
Joined
Dec 31, 2017
Messages
104
Reaction score
0
Points
16
Location
NJ
Vehicle Year
1999
Make / Model
Ranger Off Road
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Tire Size
245 75R16
havent' looked at the truck till tonight. Started up fine and ran around the neighborhood. Watched the O2 sensor voltage readings on torque.

There were 6 O2 monitors available.
O2 1x1 showed varying voltage between 0 and 1
02 1x2 was the same
02 1x3 no reading

02 2x1 was 0.0 for almost the entire ride, about a couple miles into the 3 mile loop it went to 0.1 back to 0.0. When I stopped the car and let it idle to check something outside, it started to show .3 .4
02 2x2 was steady at 1.2
02 2x3 no reading.

so I guess 02 1x1 is the passenger side forward sensor
02 2x1 is the driver side? reading 0.0 most of the time
02 1x2 is probably the sensor after the cat, not sure what 2x2 is.

The truck has california emissions, so it looks like there are two sensors and two cats before the exhaust combines, one more cat and the final third

This weekend I am going to check the wiring and pull the driver's side sensor
 

backporch

Member
Joined
Dec 31, 2017
Messages
104
Reaction score
0
Points
16
Location
NJ
Vehicle Year
1999
Make / Model
Ranger Off Road
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Tire Size
245 75R16
Does it make sense that an O2 sensor would read 0.0v while idling for a while and for most of the duration of a very short trip only to start showing a reading just before shutting the engine off?

Asking for anyone's opinion if this points toward a faulty 02 sensor, wiring or ECU.. or indicates that any of those is probably working.
 


Top