Help! Check engine light. - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 01-08-2016
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Help! Check engine light.

I have an 04 3.0 with a 154,00 miles. About a week and a half ago my check engine light came on steady, not flashing.
Made a trip to the parts store and had them pull a code. They said it was a Throttle position sensor. Changed that and reset light, came back on within 5 miles.
Went back and they confirmed the same code. They recommended a trip up the road to a small repair shop with a better code reader. They pulled a code that said Mass air sensor. Changed that, reset light and it came back on in 5 miles.

I'm needing some recommendations on whats next. Auto Zone said more than likely based on the mileage look at the throttle body.

I'm not opposed to taking her to the shop but i know more than likely it will several hundred dollars or more if it is the throttle body.

Trying to make her last till the end of the year but my inspection sticker is due and it has to pass emissions to get tags next month.

Was hoping for some suggestions before taking to major shop for detailed checkout.

Truck runs great, maybe a little slight rough idle but i can't tell anything is wrong.
What' next?
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Old 01-08-2016
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Can you remember the code numbers?

There will be about 6 codes for "Throttle position sensor" and only 1 of them means TPS should be tested or replaced.

Same for MAF(mass air flow) sensor.

Trouble codes rarely mean a sensor has failed, they actually mean sensors are working and detected a problem, if a sensor did fail the CEL(check engine light) probably wouldn't come on, lol, engine would just run bad.

So grain of salt, get the exact code number then look it up, if TPS or MAF is mentioned it doesn't mean they are bad it means they detected a problem so are working.

There is actually a code that says basically "MAF and TPS do not match"
P1112 "Throttle Position Sensor Inconsistent with Mass Air Flow Sensor"
WTF that mentions both better replace them...................

Don't feel too bad about replacing sensors and getting codes back.
90% of sensors replace by us DIYers weren't bad, so you are in good company

But........50% of sensors replaced by Professional Mechanics weren't bad, lol, I think most of that was to pad the bill though, but could be lack of training as well.


If you have a smart phone, android or apple, you can get a Bluetooth OBDII reader, they range in price from $25 to $95, make sure app is free.
These plug into ANY north american vehicle 1995 and newer, so not just a Ranger or Ford tool.
They are wireless(bluetooth), you can read codes of course but also watch live data while driving, which can be very helpful if engine is running oddly.
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Old 01-08-2016
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Thanks for the reply. I will look into this Bluetooth reader. Parts store plugged their readers into there computer to read codes. Not knowing better i didn't look at code numbers.
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Old 01-08-2016
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Just ordered code reader for I Phone. Will be here tomorrow! Thanks Again!
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Old 01-09-2016
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Very handy to have a reader that works on any vehicle made after 1995.
Help for friends and family as well, since pretty much everyone has a car/truck, lol.

Code numbers are written in computerese, they assume the person looking at the code number understands how simple computers "think", and vehicle computers are very very simple, they are basically a low speed calculator, 15-45MHz speed.
Your Iphone runs at 1.3GHz speed, that's 1,300MHz

So in the computer world this is a very very slow and simple calculator, vending machines are "smarter", lol.
But these types of computers last a long long time, and do a good job.
Because of this limited "mentality" the computer sees everything as black or white.
It has parameters(ranges) in memory, if it checks a parameter and it is out of range then it will store that parameters code in memory, when it checks that same parameter again and it is out of range again it will store code again, this will go on for a while until computer reaches another parameter that tells it to turn on the CEL to notify driver of the repeating code number, or numbers, and it is different for each code number, so it isn't "if 3 times" turn on CEL, could be 1 time turns on CEL or 10 times turns on CEL, that part is set by the program in the computer.

So it isn't an immediate "out of range turn on the CEL" reaction.
All the sensors or monitored devices in the vehicle will go out of range once in awhile, that's just the nature of electrical devices in a variable voltage system.
So computer looks for repeating out of range issues before reporting it to the driver.

The exceptions to this "rule" is emissions systems, these codes will come on first time and every time, and are very hard to clear.

The clearing part is "drive cycles", and this applies to all codes.
When engine is cold computer runs in Open Loop, the is 1/2 a drive cycle, Open Loop means computer can't use the O2 sensors to control air/fuel mix, O2 sensors don't work until they are heated above 600degF, so computer runs engine using pre-set table of air/fuel mix based on RPM, TPS and MAF data, computer is also running a Choke Routine, rich fuel mix, high idle and advanced spark timing, which a cold engine needs to stay running.
When engine coolant temp gets above 170degF then computer switches to Closed Loop, this is the other 1/2 of the drive cycle, O2 sensors are working now and computer is using them to fine tune air/fuel mix on the fly.
This is often when CEL will come back on if something is out of range, so anywhere from 5 to 8 minutes after starting engine, depends on outside temp and driving conditions.

For some codes to stay cleared you need 2 to 5 complete "drive cycles", emission codes can take even longer.

TPS sensors have very wide parameters, because these are "Learned" values, MAF sensor is also Learned value.
This means the computer will need a few drive cycles to reLearn the new sensors parameters to reset its "out of range" values.

Last edited by RonD; 01-09-2016 at 12:09 PM.
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