Truck throws a CEL
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From: Des Plaines, Illinois
Truck throws a CEL
First post!
I just recently bought a 1990 F150 XLT Lariat for around town transport. The need for a car was too great and the price was just right. It's quite an eyesore, but I'm not too concerned with that.
What does concern me however is the check engine light that comes on after about 15 minutes of driving. The water temp is ok, and the oil guage doesn't seem to work...it's almost always dead center. There is no hesitation or funny noises (beyond that of a 17 year old beater).
I haven't had a chance to try pulling a code by grounding the STI yet, but I'd like to give it a shot over the weekend. My concern is that the check engine light goes off when you turn the truck off, and if you restart, the light vanishes, only to return another 10 to 15 minutes later.
Should I try checking the code with the truck off, or do I wait until the light comes on and then pop the hood and give it a shot? I need to go pick up a multimeter, as mine met an untimely end during a hard drop.
Any help is appriciated. Thanks!
I just recently bought a 1990 F150 XLT Lariat for around town transport. The need for a car was too great and the price was just right. It's quite an eyesore, but I'm not too concerned with that.
What does concern me however is the check engine light that comes on after about 15 minutes of driving. The water temp is ok, and the oil guage doesn't seem to work...it's almost always dead center. There is no hesitation or funny noises (beyond that of a 17 year old beater).
I haven't had a chance to try pulling a code by grounding the STI yet, but I'd like to give it a shot over the weekend. My concern is that the check engine light goes off when you turn the truck off, and if you restart, the light vanishes, only to return another 10 to 15 minutes later.
Should I try checking the code with the truck off, or do I wait until the light comes on and then pop the hood and give it a shot? I need to go pick up a multimeter, as mine met an untimely end during a hard drop.
Any help is appriciated. Thanks!
Junior User
Joined: Jul 2006
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From: NE NC
The computer will keep a memory of the codes it got over the last 40(80 on some) driving cycles. When you do the KOEO(Key On Engine Off) test, it will give you the codes it is getting right then(or 1 1 for nothing wrong) then there will be a pause and the codes that are in memory will be given. Look the codes up in the manual if you have one or post them here and I'm sure someone can translate them.
Fleet Owner
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From: Easton,Ks
The oil gauge sender is a switch and the gauge acts like a light, on or off, normal or zero.
You do not need the meter, just use your CEL.
Ground the STI, get in the Cab with pin and paper, turn on the key and start counting.
These two links below may help:
This is good for the KOEO test:
http://fordfuelinjection.com/?p=13
This one is good for the KOER test:
http://www.broncodata.com/tech/codes.htm
You do not need the meter, just use your CEL.
Ground the STI, get in the Cab with pin and paper, turn on the key and start counting.
These two links below may help:
This is good for the KOEO test:
http://fordfuelinjection.com/?p=13
This one is good for the KOER test:
http://www.broncodata.com/tech/codes.htm
Last edited by subford; Jun 1, 2007 at 08:58 AM.
Fleet Owner
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From: Easton,Ks
Originally Posted by Virto
Thanks a lot guys, I'll give it a shot either today or tomorrow when I'm off work.
Is either test better suited for this, be it engine off or engine on?
Is either test better suited for this, be it engine off or engine on?
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Posting Guru
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From: Des Plaines, Illinois
I'm thinking of running out and trying the tests on lunch while I've got the truck in the big open parking lot. I don't have a roll of wire on me, but I read somewhere that you can ground the STI to the self test return with a paper clip. Would that work, and if so, will it kill me when I stick a paperclip into the terminals?
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no, you can do it with a paper clip it will work fine, might take longer than your lunch hour if there are a lot of codes though 
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From: Des Plaines, Illinois
Ok, interesting development.
Upon opening the hood for the first time in the week I've owned the truck, I discovered not a 4.9L i6, but a 5.0L V8.
I was under the impression that the truck was only available with the 4.9...so is this a previous owner swap in, and if so, could that be a cause of the CEL?
I tried to pull codes but the connectors are different. There appears to be an ECC plug attached to a long plastic cover with FUEL PUMP and some other things in raised letters. On the right side of the assembly is a small covered plug which I imagine is the STI. The cover seems zip tied in place and I don't have any new ones right now so I'm hesitant to cut it open. Anyone seen anything like this before?
Upon opening the hood for the first time in the week I've owned the truck, I discovered not a 4.9L i6, but a 5.0L V8.
I was under the impression that the truck was only available with the 4.9...so is this a previous owner swap in, and if so, could that be a cause of the CEL?
I tried to pull codes but the connectors are different. There appears to be an ECC plug attached to a long plastic cover with FUEL PUMP and some other things in raised letters. On the right side of the assembly is a small covered plug which I imagine is the STI. The cover seems zip tied in place and I don't have any new ones right now so I'm hesitant to cut it open. Anyone seen anything like this before?
Post Fiend
Joined: Mar 2002
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From: Bonita Springs FL
The truck could have come with either a 4.9L, 5.0L, or 5.8L.
The connector comes out from underneath the plastic cover. Once you pull it out you'll see the right connectors. Cut the zip ties if you have to. I leave mine hanging there without issue.
The connector comes out from underneath the plastic cover. Once you pull it out you'll see the right connectors. Cut the zip ties if you have to. I leave mine hanging there without issue.
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From: Des Plaines, Illinois
Blah, what a hot and crappy day to do this.
Ok, I've just finished pulling my engine codes and this is what I came up with. Bear in mind I'm totally new at this and might have screwed up, but I did each test twice and I think I got it right.
KOER -
41 EGO Sensor Lean
13 - Cannot control RPM during low RPM test
77 - Operator Error during dynamic response check or cylinder balance test
KOEO -
31 PFE/EPT/EVP low / EVP out of range voltage during self test
41 EGO sensor lean
67 NPS open with A/C on during self test / A/C clutch on during self test
Now, the reasons I'm not so sure about my code skills is that my a/c was certainly not turned on, and the caption says (83 2.3l turbo). Also for 31 the caption reads (2.3l and 3.8lcfi).
Any thoughts. So much for cut and dry to me anyway.
Ok, I've just finished pulling my engine codes and this is what I came up with. Bear in mind I'm totally new at this and might have screwed up, but I did each test twice and I think I got it right.
KOER -
41 EGO Sensor Lean
13 - Cannot control RPM during low RPM test
77 - Operator Error during dynamic response check or cylinder balance test
KOEO -
31 PFE/EPT/EVP low / EVP out of range voltage during self test
41 EGO sensor lean
67 NPS open with A/C on during self test / A/C clutch on during self test
Now, the reasons I'm not so sure about my code skills is that my a/c was certainly not turned on, and the caption says (83 2.3l turbo). Also for 31 the caption reads (2.3l and 3.8lcfi).
Any thoughts. So much for cut and dry to me anyway.
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From: Des Plaines, Illinois
Originally Posted by subford
Sounds like your EGR valve may be stuck open.
Is the truck safe to drive for a couple weeks until I can afford a new part, and would it makes sense for the truck to display a CEL only after 10 to 20 minutes of driving if it's the EGR?
Sorry, I'm unfamiliar with a lot of this.
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It's looks like its the egr position sensor - not the valve itself. (Low voltage code 31)on my 460 the position sensor was $35 - takes about 15 minutes to replace. if it's the valve -$80, if it's the solenoid to the valve - $110. all three -220. The test checks if the air conditioner clutch switch works -even ifyour a/c is off - in this case, it couldn;t get the switch to fire so it produced code 67.
The reason your CEL comes on after 10 minutes is the code 41. Oxygen sensor is not swithcing after the car warms up so the computer thinks it is running lean and the PCM is staying in open loop mode. = code 41 . About 60$ for a new one and they can be very easy or very hard to replace depending on if they frozen on the exhaust pipe. It's okay to drive for a while but your getting very poor performance/mileage and you probablycan't pass emissions test.
The reason your CEL comes on after 10 minutes is the code 41. Oxygen sensor is not swithcing after the car warms up so the computer thinks it is running lean and the PCM is staying in open loop mode. = code 41 . About 60$ for a new one and they can be very easy or very hard to replace depending on if they frozen on the exhaust pipe. It's okay to drive for a while but your getting very poor performance/mileage and you probablycan't pass emissions test.
Last edited by bustedflush; Jun 2, 2007 at 05:09 PM.
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Yhea, if the O2 sensor isn't working, I'm sure emissions would be impossible in Illinois. I'm kinda cash strapped for the next month, but which would you recommend replacing first, the EGR position sensor or the O2 sensor...I assume O2.
As for the A/C, it doesn't blow cold. The belt turns the compressor but I get nowhere. I assumed it was out of coolant. Does the error relate to the switch inside the cabin or is there an interal switch on the compressor that's failing? I'd like the air to work thru the summer but the daily get up and go ability of the truck is far more important...I can sweat if I have to.
As for the A/C, it doesn't blow cold. The belt turns the compressor but I get nowhere. I assumed it was out of coolant. Does the error relate to the switch inside the cabin or is there an interal switch on the compressor that's failing? I'd like the air to work thru the summer but the daily get up and go ability of the truck is far more important...I can sweat if I have to.