Question about 1990 Chevrolet C1500

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I want to check obd1 codes on 91 chevy pu i was told i could run a jumper between two terminals to get codes without scanner but which two?

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Under your dash where the ALDL is located the rectangle plug on the drivers side you take a jumper wire and jump it with the key off from the test terminal to the ground terminal the two upper right plug holes then turn the key on DO NOT START IT!!!!! then the service engine soon light will flash code 12 it will be one flash a short pause then two flashes after another slightly longer pause the code will repeat itself two more times that says the diagnostic syatem is working if there is nothng wrong 12 will repeat itself over and over but if there is a problem it will flash the code 3 times then code 12 3 times and the next code if there is more than 1 code stored then you can look in a haynes manual or manual of the sort and it will tell you which each code is or you can go to an auto parts house and they can hook it up to the scanner for free then tell you what you need

Posted on Aug 02, 2008

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Iv got a 1987 chevy celebrity it will crank up good but idling is the probleb


How long since a tune-up? Can you check for applicable trouble codes? Your obd1, you should be able to check some codes, yourself, if there are any.
To check for codes, you use a jumper wire between the A & B terminals at the datalink connector. Then, turn key just till the dash lites come on, no further. Hopefully the mil on the dash starts flashing, you count the flashes to get the codes. Your looking for two digit codes.
The basics for a rough idle is to check for a leak of some kind, fuel--egr--vacuum leak. Also, check and clean the throttle body and idle air system, see if it helps? There could be other issues?

Jan 20, 2016 | Cars & Trucks

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How do I read trouble codes for 91 geo storm? Scanners are to new to read.


that is true.
but some cars running obd1 , can be scanned,. (i have one)
like all GM cars and even older, , some ford, , Honda's . Toyota;s
but this car is GEO, (underdog, but is really what. a Isusu.)
Isuzu's cars are mostly not raced or sold here now. so who's going to make scanner for such a rare car and engine and EFI?
there is no OBD1 standard, each company uses a unique design.
then,... so...
OBD2, in 1996 a USA invention is a standard and all tools work.
so....
what you have is the old blink codes. wink wink...
all OBD1 cars work like this (or very close)
you connect a jumper wire, and the CEL lamp flashes codes.
so is the CEL stuck on? running.
must come on key on, bad lamp or bad ECU.

you can check out Isuzu Impulse

Example storm post..OBD1991 (USA)
To put the ECM (Engine Control Module/Ignition Control Module/Engine Computer) into diagnostic mode, where it will flash codes at you using the "MIL" (Malfunction Indicator Light or "Check Engine" light), short pins 1 and 3 of the ALDL/OBD1 connector using a paperclip. When you then turn the key into the on position, the MIL should flash once, then pause a bit, then flash twice. That means code "12." If there are other codes, they will be flashed out as well. All codes are two digits.
end quote, on storm

but where is the connector DLC?
and which pin is 1 an 3
so. we google more, or look it up in alldata.com like most do.

or here
http://www.robietherobot.com/storm/stormFAQ.htm

that was the 1st google hit, using clear text human questions.
DLC jumper storm or Impulse.
or diagnostic jumper Impulse.

join a Geo storm or inpulse forum and ask for scan tools.
they will be custom tools. (or hacked, as i have done)

Sep 17, 2014 | 1991 Geo Storm

1 Answer

How to get code without obd1


A 1995 model Buick should be OBD2 which would require a scanner or code reader. If it is an OBD1 system you can jumper two terminals on the test plug to make the warning light flash.

Sep 07, 2012 | 1995 Buick Century

2 Answers

On a 1995 chevy corsica can u check the codes without a scanner


UNLESS ITS A LATE 1994 MODEL WITH A GM1 PLUG THEN NO U CANT. 1995 WAS THE BORDER LINE YEAR WHEN ON BOARD DIAGNOSTIC STARTED(OBD). U CANT CHECK OBD WITHOUT A SCANNER. YOUR LOCAL AUTOZONE CAN READ THE CODES FOR U FOR FREE

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When I plug my scan tool into the computer of my 95 S10 jimmy, there is no communication. I tried replacing the omputer and got the same.


Okay, what you may have on your hands here is what has become known as an obd1.5 computer setup. Some of the 94's and 95's were made in anticipation of the switch to the obd2 set up. To determine if you fall in to this category locate your vehicle's computer. If it is under your hood in the engine compartment and you have two oxygen sensors and the port for your scanner fits an obd2 scanner then you have an obd2 system and your inability to link is either an electrical issue or something wrong with the computer itself.

If the computer is not in the engine compartment, you have one oxygen sensor, and the port for your scanner is rectangular you have an obd1 system.

If your computer is not in the engine compartment, you have one oxygen sensor and you have an obd2 scanner port you have an obd1.5.

Obd1 systems can be checked with an obd1 reader or much more easily with a paper clip or jumper wire. Just google something to effect of obd1 paper clip method. If there is still no communication once again you more than likely have an issue with your computer or electrical system.

If you have a true obd1.5 system do not fret there is still hope :) Yes there are some obd2 scanners that will work on these and there are some reportedly fancy obd1.5 code readers, however the easiest (and least expensive) way to pull the codes from this system is to use a modified version of the paper clip method. Instead of using your paper clip or jumper wires on terminals A&B, jump terminals 5&6.

Look at your scanner port. Count the terminals on the top row starting from the left. There should be connections in terminals 4, 5, and 6. Connect the jumper to terminals 5 and 6 and turn the key to the 'on' position (without turning the engine over). Your check engine light will flash. Each code will be two digits long and will flash three times (sort of like morse code). The first one will be a 1 and a 2, thus code 12. This code can be overlooked as it is just stating that the computer is being jumped. The codes that follow are the ones you should take note of.

These two digit codes correspond to the two digit obd1 codes. You can find their definitions on any number of websites. I personally prefer the haynes troublecode book though as it includes some make specific information.

Good Luck!

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3 Answers

Aldl obd1


The jumper set should be the upper top right 2 pins. Sometimes the outside of the pin can be broken, however if you place your jumper ( I've even just used a paper clip) inside both terminals, it should give you a response. Make sure your jumper is placed firmly inside of both terminals, then turn your key.

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1 Answer

How to read engine cose 1990 ford escort 1.9


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Ford owners can check their check engine light using the diagnostic connector located at the engine compartment by the fender near the battery. Getting the obd1 codes need a couple of tools: a 4 inch long gage 16 jumper wire and a 12 volt test light. Both tools are hooked up to the diagnostic connector and when the IGNITION KEY is turned on (without starting engine) the codes will begin to flash in the test light, not in the dash panel. If there is no code, you will normally get code 11 or 111. On Fords, there are 2 test modes, the KOEO (key on engine off) and the KOER (key on engine running). Both test modes should be used to get the accurate evaluation of the stored fault codes.
Most of the codes can be erased or cleared by disconnecting the battery negative terminal for 1 minute and reconnect. Just make sure to check your service manual in case you have electronic equipment such as radio or clock that needs reprogramming in which battery disconnection is not recommended. Finally after performing repairs on the culprit code, always go for a road test to confirm if the problem is fixed.
http://www.troublecodes.net/Ford/88-951325.shtml

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1 Answer

95 park avenue, how do I read the obd1 codes thru the car


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91 chevy blazer 4.3 won't start after running.


check your air filter, may have picked up dust and air flow is restricted

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