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P0155, P0135, P0141, P1131, and a crap idle.


100Timelord

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I just bought a good condition 71k 97 Ford Ranger, but I can't even get it registered right now because it won't pass emissions in this state.
The P0155 code is stored and all the rest are pending-I just switched out the 02 sensor for the P0155 code (because that's what the previous owner told me the problem was), cleared the codes, but now they've all come back. I'm thinking it's got to be a vacuum leak, and possibly an electrical issue.

P0135 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P0141 02 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2)
P0155 02 Sensor Heater Circuit Malfunction (Bank 2 Sensor 1)
P1131 - Lack of Upstream Heated Oxygen Sensor Switch Sensor Indicates Lean Bank 1

The reason I think vacuum leak is that it idles quite rough, and doesn't seem to hold fuel pressure over time. If I go to just crank it on cold start it won't fire, but when I prime the pump (and I hear it working hard to send fuel on first prime), then it'll fire up. And also, rough idle is uneven, it starts idling quite high, almost 2000rpm, but then settles and is very shaky/jerky.

So... do I have to spray the whole intake manifold down with carb clean or is this just a magic fuse issue?

Thanks!

**UPDATE: Tested the Power Distribution Box (engine bay fuse box), 15 amp HEGO fuse was intact. No dice there, sadly.
**Update 2: I forgot to mention it's running very rich--as in, it smells like a lawn mower.
 
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RonD

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Welcome to TRS :)

O2 sensors have 2 separate parts inside
The sensor part that generates its own power, 0.1v to 0.9v so under 1 volt
The heater part, the O2 sensor part can't work until it is above 650degF, so real HOT, so they are heated to get up to temp faster so computer can use them for fuel mix feedback

The three O2 heaters all share one 12volt power wire from Fuse 3 in engine bay(1997)
Then each O2 heater has its own Ground wire that runs back to the computer
The "heater code" means the computer doesn't "see" the 12volts passing thru the heater coil with key on

Since you have 3 heater codes the most likely explanation is that none of the O2 heaters have 12volts with key on
Fuse might be OK, but you need to test that the fuse has 12volts with key on
So pull out the fuse and test its 2 connections in fuse box, one connection should have 12v with key on, thats 12v IN from PCM Relay, the other connector for fuse is 12v OUT to O2 heaters

The OUT wire is light blue/orange stripe, you will see that color wire at each O2's 4 wire connector, and can check for 12volts on that wire with key on

When testing voltage you need a reference, so after you turn the key on, test battery voltage, if its 12.5volts, then you should see 12.5volts at any other 12volt connection, if you see under 12.5volts that could mean a corroded connection
If voltage is less with "no load" on the circuit then it could drop to under 5volts with a load, so "close enough" doesn't mean its OK


The rough running on Cold start wouldn't be related to the O2 heater issue, as said O2s need to be HOT to work so computer ignores them on cold start, then will start checking them once coolant is above 150degF to see if they are outputting a voltage that's "in range", "makes sense"

In a 1997 there is a fuel pressure regulator(FPR) on the engine, these can leak and extra fuel will be sucked into the engine
There are two fuel lines that come into the engine bay from drivers side frame rail
One runs to the Fuel Rail, this is the IN from the pump and filter
The other is the Return fuel line, its connected to the FPR, FPR looks like a small can and has a VACUUM HOSE attached
Check that vacuum hose for gasoline, shouldn't be any of course, if there is replace FPR, thats whats causing the Rich running
 
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100Timelord

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How do you recommend testing the two connections? I have a multimeter on hand. Just test the voltage across the two leads, or test them both to ground?

Battery is low @10.4v (though when alternator is running it does charge at ~14.6v). Should I charge the battery first and go from there?

Thanks for the welcome, I'm glad to join the community!

Update: I tested the fuse connectors--there's continuity across both with ignition on, but only 10v--could a bad battery be causing these issues?
 
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RonD

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10.4 volts is a bad battery, surprised it will start the engine

Car Batteries are 12.3v to 12.8v
12.8v new(can be 13.0v.....for a few weeks, lol)
12.5v after 3 years
12.3v after 5/6 years and time to watch for battery sales

12.2v and less is a failed battery, car batteries last 5 to 7 years

You will "cook" the alternator if it stays above 14volts all the time
This is often why people have to change both the alternator and the battery at the same time, because if either gets to far out of range it will hurt the other one
After start up battery/alternator should show above 14volts(under 15v), and then after 5minutes of idling or driving it should drop to under 14v, 13.5v to 13.9v is expected, this change means voltage regulator is working, and alternator won't "cook" the battery, running a 12volt battery at over 14volts for more than 15min will start "cooking it"

The low voltage on the battery may be why voltage regulator is pumping out the higher voltage all the time, if it is


Yes, for testing voltage turn key on and test battery voltage to get a Reference voltage
Then test any 12v connections for that same voltage with meter grounded to battery negative or a good metal ground on vehicle
 
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100Timelord

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Well... there's no fuel in the FPR vacuum line, and it looks to have been replaced recently.
The battery seems to be shot, as it was reading 14.5v for about 10 minutes.
The exhaust is pouring water (and possibly some fuel mixed in) from the cat, the tailpipe, and the middle exhaust gasket.
There is voltage across both fuse connectors w/ the ignition on.
 

RonD

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Is that fuel or water?
All exhaust will drip water, when you burn gasoline(H) with oxygen(O) you will get H2O(water) as a by-product
If there is also humidity(water in the air) and/or water in the fuel(rough running) then you get even more water out the exhaust

There is a simply test for leaking Fuel Injector
Turn key on
Press gas pedal down to the floor and hold it down all the way
Try to start engine
It should not fire or start, just crank
If it fires or starts then you could have a leaking injector

Above is called "Clear Flooded Engine" routine, built into ALL fuel injection computers
When computer is on(key on) and it see 0 RPMS and WOT(wide open throttle) it will turn OFF the fuel injectors, allowing driver to crank engine over to dry out a flooded engine, spark is still on

If you have 12volts at Fuse 3 then unplug any O2 sensor's 4 wire connector and test the light blue/orange stripe wire for that same 12volts
If its not there then that light blue/orange stripe wire is broken at the fuse box or close to it, before it splits off to the 3 O2 Heaters
 

100Timelord

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Hey, uh... what is this? Is this important? It looks like it plugs into the intake somewhere...
 

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100Timelord

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Did the clear flooded engine routine, it started right up no problem. The gas pedal is loose, but I set it at WOT with my finger and it still started right up. Unless the throttle is set incorrectly, it seems to have failed the test.
 

100Timelord

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Hey, uh... what is this? Is this important? It looks like it plugs into the intake somewhere...
Nvm I'm 99% sure it's the cruise control module. Hopefully it's not the one that was recalled though... I don't know why it was sitting, unfastened, in the engine bay.
 

100Timelord

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Thanks for the help Ron. I'm gonna send it to a qualified mechanic tomorrow and I'll post an update with the bad news.
 

RonD

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So you may have leaking injector, once engine fires enough to reach 400rpms computer will turn all injectors back on
Cranking speed is 200rpms

Give the mechanic those codes, it will help him or her
 

Tater55

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Thanks for the help Ron. I'm gonna send it to a qualified mechanic tomorrow and I'll post an update with the bad news.
Hey @100Timelord, just reading through your thread. I have a 2000 3.0 4WD 5spd ranger. I had exactly, and I mean EXACTLY, the same symptoms you’re having. From the rough idle, to the leaking exhaust, to the same four codes. I replaced everything I could think of until the engine ultimately lost compression so I had to tear it down.
I took the heads off and took them to a machine shop. I was going to install them back on but decided to take out the whole engine instead and do a full rebuild. I currently have the engine block, crank, and flywheel at the machine shop getting worked on. I did this in hopes of fixing this issue, but I have a suspicion that it’s going to be an electrical issue. I’m pretty sure I’m going to have to end up replacing the ECM. Please update us on your truck as well, this will definitely help me out moving forward. Thank you!
 

100Timelord

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Finally, an update:

Ok, I've had it in and out of the shop a few times, but the issues presented in my first post are finally solved!

The poor idle/not holding fuel pressure was because of a faulty fuel pump. I'm assuming a faulty check valve, but I did not specifically ask. The fuel pump was replaced, and the idle/fuel pressure issue was resolved.

The O2 codes: When I took it to the mechanic, they found the upstream sensor on the passenger side (opposite the side I replaced) was UNPLUGGED! Kinda shows the quality of care this Ranger has gotten thus far. They plugged it back in, but the codes came back, so they suggested I warranty the NTK O2 sensor I installed previously. I replaced the NTK with a GENUINE FORD MOTORCRAFT™️ Bosch sensor, but rge codes came back again.
I returned it to the shop, and they diagnosed a faulty ECM. They installed a remanufactured ECM, and the O2 heater gremlins have not returned thus far.

I'm now having a transmission issue, but that's a story for another thread. Hope some of this helps someone 👍
 

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