1997 Ford Ranger XLT 185,000 miles - has sat off and on for extended periods of time. Runs and drives okay but I'm getting about 10 MPG at the moment.

Check engine light had been on for a while and I think I might have burned it out because it's not showing up anymore. I took my chances and tried to pass DEQ and to no surprise, it failed to pass.

Here are the error codes. Any advice? I've purchased 3 new O2 sensors and I plan on replacing them.
I've been reading some forums and copied a very helpful reply from 2014.

P0340 "CAMSHAFT POSITION SENSOR "A" CIRCUIT - BANKE 1 OR SINGLE SENSOR
P0135 O2 SENSOR HEATER CIRCUIT - BANK 1 SENSOR 1
P0141 O2 SENSOR HEATER CIRCUIT - BANK 1 SENSOR 2
P0155 O2 SENSOR HEATER CIRCUIT - BANK 2 SENSOR 1
P1132 LACK OF UPSTREAM HEATED OXYGEN SENSOR SWITCH - SENSOR INDICATES RICH - BANK NO. 1
P1152 LACK OF UPSTREAM HEATED OXYGEN SENSOR SWITCH - SENSOR INDICATES RICH - BANK NO. 2

Should be a fuse in engine fuse box that powers all 3 of the heaters in the O2 sensors, the computer monitors that heater voltage and no voltage is what sets those codes.
If there was only one O2 sensor with that code then I would suspect wiring or the heater in the sensor was bad.
But all 3 is most likely a blown fuse

That may also solve the Rich codes

The Bank 1 sensor 2's usually lasts the life of the vehicle, it should only "see" clean exhaust being located after the Cat Converter.

The Bank 1 and Bank 2 sensor 1's get the straight exhaust from the engine and are usually OK for 150k miles, spec is 100k.
MPG tends to go down as these O2s wear out, but it doesn't cause major issues, just costs you more money in fuel.

Clean the MAF sensor, always.

Rich code means the computer has cut down fuel injector open time to a pre-set limit(which sets that code) and O2 sensors are still showing less Oxygen content(rich) in exhaust than it should.

Because engine sat for awhile you could have a few fuel injectors that are sticking, letting in too much fuel.
A few because if it was just one then only 1 bank would show Rich code
Run some Seafoam, or similar, injector cleaner in the gas tank that should help clean them up.

On the fuel rail there is a fuel pressure regulator(FPR), passenger side top front of engine, the Return Fuel hose is connected to it, and also a vacuum hose.
Pull off that vacuum hose and check it for fuel, or start engine with it off and see if fuel comes out of FPR, it shouldn't of course.
It it sat dry the rubber in the FPR diaphragm may have cracked and is leaking, and the vacuum line sucks that extra fuel into the intake causing both banks to run rich

Is the exhaust showing black smoke after it is warmed up?

 

1997 Ranger uses Fuse #3 in engine bay fuse box to power the O2 sensor heaters, yours is most likely blown, replace it, and make sure it doesn't blow again, if so you have a melted/shorted O2 sensor wire

All these codes are caused by blown Fuse #3
P0135 O2 SENSOR HEATER CIRCUIT - BANK 1 SENSOR 1
P0141 O2 SENSOR HEATER CIRCUIT - BANK 1 SENSOR 2
P0155 O2 SENSOR HEATER CIRCUIT - BANK 2 SENSOR 1
P1132 LACK OF UPSTREAM HEATED OXYGEN SENSOR SWITCH - SENSOR INDICATES RICH - BANK NO. 1
P1152 LACK OF UPSTREAM HEATED OXYGEN SENSOR SWITCH - SENSOR INDICATES RICH - BANK NO. 2

O2 sensors only last 100k miles or 12 years, so not a waste of money to replace them when they are older, your 1997 is 25 years old so should be on at least the 3rd set of O2s

1997 Ranger has a Fuel Pressure Regulator(FPR) on the engine, last year for that
There will be 2 fuel lines coming in to the engine bay on drivers side
Follow both
One will go to a small can that also has a Vacuum hose attached, the "can" is the FPR
Remove vacuum hose and check it for gasoline, if found replace FPR
Leaking FPR causes raw gasoline to be sucked into the engine causing rough running a very very low MPG



Once the above has been fixed, you can then look at the Cam sensor code
P0340 "CAMSHAFT POSITION SENSOR "A" CIRCUIT - BANKE 1 OR SINGLE SENSOR

On the Ranger 3.0l engines this was a fairly common code when the Cam Synchro unit was failing
Its at the top rear of engine, and can make a "squeaking" noise when its starting to fail
Not hard to change but it is a TIMED part, so it needs specific placement to work correctly

 

I am working through the same error codes as adamdude but on a 1997 Aerostar 3.0l v6.

Are Aerostar O2 sensor heaters also fused? I assume so but can not find a fuse listed in the interior fuse box.

 

Fuse will be in Engine Bay fuse box, not in interior fuse box
Often labelled HEGO or HO2S

 

Thank you for your reply RonD.

Seems I'm looking on the wrong side of the firewall! Was unaware of a fuse box in engine bay. Have only seen a relay bank near the battery so will have to look more closely.

Cheers, Fraser

 

Never owned an Aerostar so can't say but never ran into a vehicle without an engine bay fuse box, yes relays in there as well

Ignition switch needs a fuse close to battery, usually 50amp, and other full time fuses in cab fuse box also need a fuse near battery, also 50 amp
Then a fuel pump fuse, PCM(computer) fuse and O2 heater fuse

Fuses all need to be as close to the power source as practical, in this case, the battery
If they ran a wire from battery to ignition switch with no fuse on it, then the WIRE is the fuse, so if there was a short then there would be a FIRE
So they put a 50amp fuse on it, and when ignition switch is on that 50amp 12volts feeds several other fuses in the cab fuse panel, and those fuses protect each wire that run to the device being powered, these fuses are usually 5 to 20amps

 

According to the owners manual, a 97 Aerostar just has the inside fuse box and some fusible links coming from the starter relay

Owners manual available here
https://www.fordservicecontent.com/F.../97aerog1e.pdf

Fuse info on pages 200 to 209

 

RonD, thanks for explanation. Understand need for fusing circuits, just hadn't seen a fuse box in the Aerostar engine compartment.

2011Supercab, that explains why! Found several fusible links below the starter relay, somewhat hidden by the battery. Will start there.

Thank you both.

 

Hi Ron D,

I replaced all the O2 sensors. I replaced the large fuse #3 in the Engine Bay Fuse box as well.
I need to move on to the FPR and Cam Sensor next. Also, having a rough idle issue when I place the transmission in neutral while driving. Engine REVS to 3000RPM on its own.

I will follow your advice and check the FPR next. You're a legend RonD!

1997 Ranger has a Fuel Pressure Regulator(FPR) on the engine, last year for that
There will be 2 fuel lines coming in to the engine bay on drivers side
Follow both
One will go to a small can that also has a Vacuum hose attached, the "can" is the FPR
Remove vacuum hose and check it for gasoline, if found replace FPR
Leaking FPR causes raw gasoline to be sucked into the engine causing rough running a very very low MPG

Once the above has been fixed, you can then look at the Cam sensor code
P0340 "CAMSHAFT POSITION SENSOR "A" CIRCUIT - BANKE 1 OR SINGLE SENSOR

On the Ranger 3.0l engines this was a fairly common code when the Cam Synchro unit was failing
Its at the top rear of engine, and can make a "squeaking" noise when its starting to fail
Not hard to change but it is a TIMED part, so it needs specific placement to work correctly