CEL came on, a few codes, not sure...

[jlarocque]

Here are the codes: P0231, P1000, P0133, P1131 and P0171. My truck has 198k miles on it. Should I start by changing the O2 sensor? And I have no idea about the P0231 code... any advice? Thanks.

 

[AzLizard]

My po171 code was as split fuel line off the pump.
Twice.

 

[RonD]

What year is the Ranger 3.0l?
2WD or 4WD?
Manual or automatic?

P0231 - Fuel Pump Secondary Circuit Low
The Computer(PCM) controls the Fuel Pump Relay, it closes this relay to send power to the inertia switch which passes power to the fuel pump.
The PCM has a wire connected to the Inertia switch terminal so it can "see" if 12volts is there after it closes the Relay.
So P0231 means power is not there or very low after relay closes.
You can pull out the Fuel Pump Relay, in the engine fuse box, and check to make sure contacts are clean, then plug it back in.
If you are actually losing power to fuel pump, engine would stall instantly, so could be loose wire at inertia switch or PCM



P1000 - OBD-II Monitor Testing Incomplete
For Ford this just means battery may have been unhooked or OBD Codes were cleared and PCM has not had a chance to retest all the systems it monitors.
So not a problem code

P0133 - 02 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P1131 - Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P0171 - System too Lean (Bank 1)

These 3 codes involve the one O2 sensor on Passenger side exhaust pipe close to the engine.
Bank 1 = Passenger side
Bank 2 = Drivers side
Sensor 1 = closest to engine, also called Upstream sensor
Sensor 2 = Behind Cat Converter, called Downstream sensor(tests if Cat is working, cleaning exhaust)

I would certainly check the connector and wires on that O2 sensor, and make sure sensor is tight, screwed in, they can loosen up.

O2 sensors see Oxygen in the exhaust, not fuel, so an exhaust manifold leak on passenger side will suck in air, so will cause these codes
O2 sensors generate their own voltage, they are heated with 12volt power, but the sensor part generates .1 to .9volts
.1volt if there is too much oxygen, Lean
.9volt if there is too little oxygen, Rich

PCM uses air flow data from MAF sensor to calculate 14.7:1 air:fuel ratio in real time while driving
PCM constantly changes fuel mix so O2 sensor voltage will change 3 or 4 times a SECOND, not minute, PCM tries to keep O2 voltage between .3 and .5, sweet spot.
If O2 shows .2v PCM adds more fuel to that Bank, and expects that O2 to respond with an increase in voltage, say .5v
If that doesn't happen PCM adds even more fuel to that Bank, and sets code P0133 - 02 Sensor Circuit Slow Response (Bank 1 Sensor 1)
If it still doesn't change after adding more fuel then it sets code P1131 - Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1

P0171 - System too Lean (Bank 1) is set because O2 voltage is low, Lean

Upstream O2 sensors usually need to be change every 150,000 miles, they pay for themselves in MPG, as O2 sensors get older they start to show False Lean, so PCM runs engine Richer than it needs to run, which costs you $$ as MPG slowly goes down.

So if they are original O2 sensors with 190k+ miles then worth changing both in any case, and might be the problem, for those 3 codes.
You don't need to change Downstream O2 sensor until it sets a code, it "sees" cleaner exhaust being behind Cat so doesn't wear out as fast, not that 150k miles is fast, lol.

 

[jlarocque]

What year is the Ranger 3.0l?
2WD or 4WD?
Manual or automatic?

P0231 - Fuel Pump Secondary Circuit Low
The Computer(PCM) controls the Fuel Pump Relay, it closes this relay to send power to the inertia switch which passes power to the fuel pump.
The PCM has a wire connected to the Inertia switch terminal so it can "see" if 12volts is there after it closes the Relay.
So P0231 means power is not there or very low after relay closes.
You can pull out the Fuel Pump Relay, in the engine fuse box, and check to make sure contacts are clean, then plug it back in.
If you are actually losing power to fuel pump, engine would stall instantly, so could be loose wire at inertia switch or PCM



P1000 - OBD-II Monitor Testing Incomplete
For Ford this just means battery may have been unhooked or OBD Codes were cleared and PCM has not had a chance to retest all the systems it monitors.
So not a problem code

P0133 - 02 Sensor Circuit Slow Response (Bank 1 Sensor 1)
P1131 - Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P0171 - System too Lean (Bank 1)

These 3 codes involve the one O2 sensor on Passenger side exhaust pipe close to the engine.
Bank 1 = Passenger side
Bank 2 = Drivers side
Sensor 1 = closest to engine, also called Upstream sensor
Sensor 2 = Behind Cat Converter, called Downstream sensor(tests if Cat is working, cleaning exhaust)

I would certainly check the connector and wires on that O2 sensor, and make sure sensor is tight, screwed in, they can loosen up.

O2 sensors see Oxygen in the exhaust, not fuel, so an exhaust manifold leak on passenger side will suck in air, so will cause these codes
O2 sensors generate their own voltage, they are heated with 12volt power, but the sensor part generates .1 to .9volts
.1volt if there is too much oxygen, Lean
.9volt if there is too little oxygen, Rich

PCM uses air flow data from MAF sensor to calculate 14.7:1 air:fuel ratio in real time while driving
PCM constantly changes fuel mix so O2 sensor voltage will change 3 or 4 times a SECOND, not minute, PCM tries to keep O2 voltage between .3 and .5, sweet spot.
If O2 shows .2v PCM adds more fuel to that Bank, and expects that O2 to respond with an increase in voltage, say .5v
If that doesn't happen PCM adds even more fuel to that Bank, and sets code P0133 - 02 Sensor Circuit Slow Response (Bank 1 Sensor 1)
If it still doesn't change after adding more fuel then it sets code P1131 - Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1

P0171 - System too Lean (Bank 1) is set because O2 voltage is low, Lean

Upstream O2 sensors usually need to be change every 150,000 miles, they pay for themselves in MPG, as O2 sensors get older they start to show False Lean, so PCM runs engine Richer than it needs to run, which costs you $$ as MPG slowly goes down.

So if they are original O2 sensors with 190k+ miles then worth changing both in any case, and might be the problem, for those 3 codes.
You don't need to change Downstream O2 sensor until it sets a code, it "sees" cleaner exhaust being behind Cat so doesn't wear out as fast, not that 150k miles is fast, lol.

Wow thanks for the great reply! Its a 3.0 2wd 5 speed manual.