Need help interpreting ODB1 codes

[The Lorax]

1994 Ranger
4.0
4x4
manual

Through some research I was able to pull codes off my truck by counting the flashing of the check engine light. But the numbers (flashes) that I've come up with don't really make sense given the other information stated about how to interpret these codes.

I've taking this reading several times before and after disconnecting the battery, and I get the same output:

5 2 2 3 4 1 then this sequence seems to repeat 5 2 2 3 4 1 then a pause and I get:
1 1 8 6 1 8 6

This is all with the engine off but key in start position. With engine on I get NO codes, the check engine light does not flash at all.

I was told that the first flashes would indicate what engine size I have but 5 does not correspond to cylinders or liters, so....

And, my research states that for my vehicle (engine) I should be using the 3-digit codes (not the 2-digit codes) to interpret these flashes. But if I look at it that way there is an uneven number of flashes with the 1 1 8 6 1 8 1 set. And I'm wondering if the first 5 is actually the start of the codes or something else.

Can anyone shed some light on how to interpret these flashes for my truck?

 

[Mazda]

Are you using a code reader or just counting flashes.

I was never good at trying to read the "flashes" on the CEL even with a simple code reader.

My suggestion would be to get one of these. You will use it often and will pay for itself in no time.

http://www.autozone.com/test-scan-a...ader/innova-ford-obd1-code-reader/273350_0_0/

Key On Engine Off - Will not give you the cylinder ID. You will only get that with Key On Engine Running.

 

[The Lorax]

Thanks all.

I took the truck down to the express lube place and they put a scanner on it for free.

Turns out the codes were just as the flashes conveyed except that the 1 was just a seperator for the two sets of codes.

So, my truck has these fault codes.

522 - Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault - PNP
341 - Octane jumper installed (information only code to notify you if it is installed)
186 - Injector pulse width longer than expected or Mass Air Flow (MAF) lower than expected - Fuel control

Additionally, the shop scanner came up with two more codes:

172 - Oxygen sensor not switching - system is or was lean - Single, Right or Rear HO2S - Fuel control
176 - Oxygen sensor not switching - system is or was lean Left or Front HO2S - Fuel control

I'm trying to pass smog, will all of these codes present (except for 341) cause me to fail smog?

 

[Mazda]

Okay to clarify

Do you have a CEL on right now? What state do you live in?

Here in California if a CEL is present they won't even start the test.

Did they also clear all the codes? Did the CEL come back on after they cleared them?

Code 186 - I would clean the MAF to start. Be carful. Search the forums to see how to do it.

Code 172,176 - How long since you changed your o2 sensors? I would change them if it's been a few years. You will also see a big jump in MPG also.

You really want to get your cat really "HOT" before you go in to pass smog. Especially with a truck as old as ours. Take it for a drive for at least 20 minutes and call the test place and see if they can test it right away when you get there. That way it won't cool down.

Bryan

 

[RonD]

522 Park/Neutral Position (PNP) or Clutch Pedal Position (CPP) circuit fault - PNP
You have a manual transmission so when scanning for codes the clutch pedal needs to be down all the way or you will get the 522, so ignore it, just like 341

186 Injector pulse width longer than expected or Mass Air Flow (MAF) lower than expected - Fuel control.

The way computer controlled fuel injection works is like this:
The MAF(mass air flow) sensor is a heated wire, the air flow passing this wire cools it down, the cooling down is changed to a voltage and computer uses that voltage to calculate the WEIGHT of the air being pulled into the engine.
Once computer has that weight is uses the air fuel mix ratio for gasoline engines, 14.7:1, 14.7 pounds of air to 1 pound of fuel, or ounces or grams, lol, but it is by weight.

That calculation is 0 on computers floating Fuel Trim chart.
After the calculated air/fuel mix is burned in the engine the O2 sensors report the Oxygen level in the exhaust, too much oxygen is a Lean Burn, too little oxygen is a Rich Burn, O2 sensor can't see fuel only Oxygen.

If O2 sensor shows Lean then computer opens injector a little longer(longer Pulse Width), and that is +1 Fuel Trim, if O2 still shows Lean then computer goes to +2, and so on.
If there was low oxygen in exhaust, Rich, then computer would shorten the pulse width to add less fuel, -1, -2, -3, ect............

When a Fuel Trim number gets up above +20 or below -20 for any length of time the computer will notify driver that the calculation it is making(0) is too far off.
It is quite normal for an older engine to be running at +6 to +10, fuel injectors are a bit dirty, fuel pressure is lower with older pump, so less fuel flows in when injector is opened.
Or a dirty MAF sensor doesn't cool down as much so computer see less air flowing in so adds less fuel, exhaust shows Lean.

So 186 is the computers way of saying there is too much air or too little fuel, and it's 14:1 calculation isn't working

A vacuum leak or a leak in the air tube from MAF sensor to intake manifold will allow "unreported air" into the engine, all the air must flow thru the MAF sensor for computer to calculate accurate air weight.

O2 sensors, well a '94 should have one on each exhaust manifold, so 2 of them.
You have codes that both show Lean, for both to fail at the same time would be very very unlikely.
These are good for 100k miles and are good to replace at that time because MPG goes down as these start to wear out.
But not likely your problem.
An O2 sensor creates it's own voltage for computer to read, 0.10v to 0.90volt, because RPMs are always changing so fuel trims must change and the O2 voltage is always changing or "switching", computer tries to keep O2 sensor's voltage at about .45, if it goes down or up computer increases or reduces the pulse width accordingly, if computer gets to a limit on the pulse width(+20/-20) and O2 sensor voltage isn't coming back to .45 it says it isn't "switching", i.e. Oxygen sensor not switching, and it is lower voltage so Lean

I would check for vacuum leak first because it is easy, not finding it, lol, but checking for it.
After engine is warmed up idle should be about 650rpms.
On the upper front side of intake is the IAC(idle air control) Valve, unplug it's electrical connector while engine idles.
RPMs should drop to 500 or engine may even stall, either is good it means no vacuum leak, if RPMs don't drop then you do have a vacuum leak.

Clean MAF sensor: http://www.therangerstation.com/tech_library/CleanMAF.shtml
Check the MAF's air tube, underside can crack, or rubber gaskets at the ends can go bad, this needs to be air tight and the hose to oil filler cap needs to be good as well, PCV system keeps engine sealed so this isn't a "leak".

Check fuel pressure, auto parts stores often loan or rent gauges
'94 should have 35-42psi at idle and stay above 30psi with engine at 2,500rpm for a minute or so.
Then engine off the pressure should stay above 25psi basically forever, but a few months anyway, so no slowing dropping of pressure with engine off.
Computer can't monitor fuel pressure, it assumes 35psi in it's calculation

 

[The Lorax]

Outstanding information Ron, thanks.

Yes, I also thought both o2 sensors being bad was an indication that the real problem was elsewhere.

I will test for vacuum leaks and then proceed to other tests.

One thing I should have mentioned, the idle is funny, it revs up and then down continuously. It is not a large rev but slight. Would that be an indication of vacuum leak?

Mazda, yes I live in california.
They did clear the codes but then when I got home I checked the again but counting the flashes and the same codes reappeared. But as with all of my manual tests the 172 and 176 don't appear. I wonder if they are engine run only tests, and why do I get no flashes when I do the engine run test?

 

[RonD]

Yes, wandering idle could be vacuum leak.
IAC Valve is a very precise way to control idle.
Computer controls it second by second, so if idle is wandering then IAC valve is moving to try and keep idle at the target RPM, based on engine temp.
A steady vacuum leak should set a steady idle though so wandering could be gasket leak that is allowing more and less air in, but just guessing.
Throttle body gasket or even throttle plate rod could do that.
PCV Valve could as well.

 

[The Lorax]

So, I unplugged the IAC valve connector and it did as it should, the engine was idleing around 650 and when I unplugged IAC it went to about 500, there was a noticeable decrease and at first it felt like the engine was going to stall.

So, what do you recommend for the next step? Should I clean the MAF? Or do some other vacuum leak test?

Thanks for you help.