• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

P1151 check engine light - 1996 ranger 4.0 - possible wiring issue


sebastian323

Member
Joined
Aug 2, 2021
Messages
40
Reaction score
4
Points
8
Location
Merced, CA, USA
Vehicle Year
1996
Make / Model
Ranger XLT
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Hello, my ford ranger has a check engine light with the code

P1151Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2

This is the only code present. i just changed the driver side pre-catalytic O2 sensor with a brand new bosch unit. The old sensor was rusted on and I had to use my torch on it. The check engine light re-occurred after the car preformed the O2 sensor readiness test. This is a snapshot of the voltages read by the ECU as a drive around. The O2 Bank 2 - Sensor 1 Voltage is constantly at zero. which sensor is this bank 2 sensor 1 ? As I understand it , Bank 2 corresponds to the driver side of the vehicle ? Would this mean the downstream oxygen sensor is named bank 1 sensor 2 ? I am afraid the problem in question may be a wiring fault if indeed the sensor I replaced is reading zero volts. my speedmoter which is on the same harness as this sensor had bad wiring which I had to redo

o2 sensors.jpg
 
Last edited:


Rock Auto 5% Discount Code: F9A1A579ACFAD1: October 1st, 2021

RonD

Well-Known Member
Joined
Jun 2, 2012
Messages
20,191
Reaction score
3,973
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
You have a wiring issue or a "dead" new O2 sensor
Possibly internal computer circuit issue

O2s are IDed like this
Bank 1(B1) = Passenger side on any "V" engine, only Bank on a 4cyl
Bank 2(B2) = Drivers side of any "V" engine

Sensor 1(S1) = Upstream O2, pre-Cat
Sensor 2(S2) = Downstream O2, post Cat

So there is
B1S1 passenger side upstream
B1S2 passenger side downstream
And that's all on a 4cyl engine
These are on a V6 or V8 engine
B2S1 drivers side upstream
B2S2 drivers side downstream

Most single exhaust systems don't have B2S2, they just have the one B1S2 after the Cats
But in the mid to late 2000's even single exhaust started seeing B2S2 added on V6 and V8


Unplug the O2 B2S1(Bank2 Sensor 1) connector and inspect it
Should be 4 wires
2 wires are for the Heater(blue/orange and yellow/blue)
And
2 wires for the sensor part

The heater circuit has its own codes, like P0155 - 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
So Heater wires are most likely OK

The 2 sensor wires are what you should look at
Orange wire and Red/Black stripe wire on B2S1
The Orange wire is the "common wire" shared by most sensors, all O2, and most of the engine sensors, its a Grey/Red wire at engine sensors, like throttle sensor, ECT sensor, IAT sensor, DPFE sensor, ect......
So you can use an OHM meter to test if Orange wire shows 0 ohms(connection) to the Grey/Red wire on one of the engine sensors

The Red/black wire runs directly to the computer, pin 87, so you could only test it there
But check that the O2 connector and it pins are OK, wires are not frayed and pins are not bent


Just FYI
O2 sensors read Oxygen levels in exhaust
Low Oxygen is Rich or 0.9volt
High Oxygen is Lean or 0.0volts

So code P1151 = Lack of HO2S-21 Switch, Sensor Indicates Lean, probably meant you had a wiring issue to begin with
O2 sensors should be changed every 100k miles or 12 years which ever comes first, after that MPG will start to go down slowly, so best to change them and keep more money in your pocket, gas ain't cheap, lol

Your downstream O2 looks like its due, 0.6volt should be running at 0.7 to 0.8volts, because Cats burn up most of the oxygen when burning up pollutants, so should be low Oxygen levels
But could also be Cats are getting old, O2s are cheaper to try, lol
 

sebastian323

Member
Joined
Aug 2, 2021
Messages
40
Reaction score
4
Points
8
Location
Merced, CA, USA
Vehicle Year
1996
Make / Model
Ranger XLT
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
You have a wiring issue or a "dead" new O2 sensor
Possibly internal computer circuit issue

The heater circuit has its own codes, like P0155 - 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
So Heater wires are most likely OK

The 2 sensor wires are what you should look at
Orange wire and Red/Black stripe wire on B2S1
The Orange wire is the "common wire" shared by most sensors, all O2, and most of the engine sensors, its a Grey/Red wire at engine sensors, like throttle sensor, ECT sensor, IAT sensor, DPFE sensor, ect......
So you can use an OHM meter to test if Orange wire shows 0 ohms(connection) to the Grey/Red wire on one of the engine sensors

The Red/black wire runs directly to the computer, pin 87, so you could only test it there
But check that the O2 connector and it pins are OK, wires are not frayed and pins are not bent

So code P1151 = Lack of HO2S-21 Switch, Sensor Indicates Lean, probably meant you had a wiring issue to begin with

Your downstream O2 looks like its due, 0.6volt should be running at 0.7 to 0.8volts, because Cats burn up most of the oxygen when burning up pollutants, so should be low Oxygen levels
But could also be Cats are getting old, O2s are cheaper to try, lol
Do the heater wires receive a simple voltage for power and ground ? can i pull the sensor out and see if it heats up ? I can inspect those with a multi-meter. In case of failed wiring, I am planning to make a jumper across the orange common sensor wire and then run a wire straight to the ECU for the signal. Thanks a lot for the information. Also, do you think I destroyed the original oxygen sensor by running a torch on it to remove it (some of the rust got red hot)

thanks for the tips!
 

RonD

Well-Known Member
Joined
Jun 2, 2012
Messages
20,191
Reaction score
3,973
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
Heater in the O2 is working or you would have another code regarding the heater in that O2 sensor
Each O2 heater has its own code that will come up if that one heater fails
But with key on engine off you can use a Volt meter to test if heater is getting 12volts and ground
Blue/orange wire is 12volt <<<only with key on
Red/white wire is a ground <<<only with key on

Yes, you use an OHM meter to see if the Orange wire is connected to one of the Grey/red wires on any engine sensor
Or see if its connected(0 ohms) to the Orange wire on the other O2 sensor, B1S1
Orange wire is a common shared wire for all sensors

Red/black wire can only be test at the computer, pin 87



I wouldn't count on the old removed O2 sensor working again, it might but if its over 12 years old its passed it usefulness anyway
 

sebastian323

Member
Joined
Aug 2, 2021
Messages
40
Reaction score
4
Points
8
Location
Merced, CA, USA
Vehicle Year
1996
Make / Model
Ranger XLT
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
Heater in the O2 is working or you would have another code regarding the heater in that O2 sensor
Each O2 heater has its own code that will come up if that one heater fails
But with key on engine off you can use a Volt meter to test if heater is getting 12volts and ground
Blue/orange wire is 12volt <<<only with key on
Red/white wire is a ground <<<only with key on
I fixed the wiring to the sensor itself by running a cable to pin 87 on the ECU and tapping power from the nearby oxygen sensor. However the nearby oxygen sensor seems to have a non functioning heater as well so when I tapped into that I did not get heater power to my new 02. My new sensor works fine without the heater once the car is warm. I hope the car can pass smog check even with the sensor unheated. At this time I am not so concerned with tthe car running 100% as I am with passing the smog so I can register it and not risk getting pulled over. I am considering grounding the heater to the chassis and powering it from the orange wire that powers the sensor.

This is what the data looks like on a cold start:
64687




And this is what it looks like once the car is warmed up.

64688
 

RonD

Well-Known Member
Joined
Jun 2, 2012
Messages
20,191
Reaction score
3,973
Points
113
Location
canada
Vehicle Year
1994
Make / Model
Ford
Transmission
Manual
In a 1996 Ranger check fuse 20 in engine bay fuse box, 15amp, that's the O2 heater fuse
 

sebastian323

Member
Joined
Aug 2, 2021
Messages
40
Reaction score
4
Points
8
Location
Merced, CA, USA
Vehicle Year
1996
Make / Model
Ranger XLT
Engine Type
4.0 V6
Transmission
Manual
2WD / 4WD
4WD
In a 1996 Ranger check fuse 20 in engine bay fuse box, 15amp, that's the O2 heater fuse
I checked the fuse and it seems to be good. I am guessing its more wiring problems, probably at the connector that sits on the back of the driver side of the engine where the wiring from the transmission comes in.
 


Top