Retrieving Trouble Codes from OBD I Systems

[BigWheel]

Not sure if this should be a sticky or not but after reviewing the Haynes manual, and others, there is nothing very clear about how to retrieve the trouble codes from the On Board Diagnostic I (OBD I) system on 1985 to 1995 Fords.

So with that said when your check engine light comes on open the hood. In the engine bay, drivers side, next to the fire wall you will find a 1 pin female connector. This is the STI terminal. Take a jumper wire, ground one end to bare metal in the engine bay and the other end should go into the 1 pin STI terminal. Turn the key on without starting the engine. Watch the check engine light as it will flash the trouble code. Long flashes will be the first number of the code, short flashes will be the second number. Short flashes only will be single digit trouble codes (example, 9 quick flashes will be code 09 which is the Coolant Temperature Sensor). This is for OBD I systems only.

Hope this helps but if not ask questions!!!!

[2002maniac]

Good info! which years have OBD1?

[Gomez]

...how to retrieve the trouble codes from the On Board Diagnostic I (OBD I) system on 1985 to 1995 Fords.

^^

[miami man]

maybe they can make a sticky for it.

[bhazard]

I thought our cars werent even OBD?

[jglutz]

OBD Started in the early 80's with athe advent of TBI. The EPA mandated the start of OBDI i '88 with full compliance by '92 and OBDII by 96.

Early on many manufacturers bastardized their connector and protocols. In the early years one of the rices (I think Datsun) had the CE light come on every 25K which could only be reset by the dealship. The feds went balistic.

GM had the ALDL (Assebly Line Data Link) connector which could be used like the Festiva STI or could be connected to with a PC in terminal mode with a RS-485 connector.

Jim D. would probalbly know better.

If this post where to to be made a sticky....it shuld include all of the trouble codes.

[FB71]

OBD Started in the early 80's with athe advent of TBI. The EPA mandated the start of OBDI i '88 with full compliance by '92 and OBDII by 96.

Early on many manufacturers bastardized their connector and protocols. In the early years one of the rices (I think Datsun) had the CE light come on every 25K which could only be reset by the dealship. The feds went balistic.

GM had the ALDL (Assebly Line Data Link) connector which could be used like the Festiva STI or could be connected to with a PC in terminal mode with a RS-485 connector.

Jim D. would probalbly know better.

If this post where to to be made a sticky....it shuld include all of the trouble codes.

very, very close, Joe.

OBD stands for On Board Diagnostics. Mandated by the federal government to alert and assist repair technician with faults.

OBDI rollout started in 1982 for the 1983 model year in California. Began with feedback carburators.

By 1986, the feds had mandated a warning lamp to alert the operator to a fault affecting tailpipe emissions. Thus begins the "Check Engine" lamp.

Every manufacturer had their own protocol, language, codes and definitions. Technicians had to know at potentially dozens of code reading proceedures, one, two and three digit codes, and code reset procedures. This also meant purchasing potentially dozens of scantools, most several thousand dollars each. This lead the feds to make a few changes.

The Kyoto clean-air treaty of '88 agreed on a scaled global rollout (with participating countries) by '92.

OBDII was mandated for North American rollout by MY '96. OBDII has many added features over OBDI, and the aforementioned changes.

OBDII mandated a global code definition. Every manufacturer now had to use the same 5-digit code for the same fault. The first digit indicates the major system of failure; P = powertrain, B = body, C = chassis, U = undefined ( a catch-all catagory). The second digit is either a 0 or 1. 0 indicates a universal code, used by all manufacturers. 1 indicates a code unique to that manufacturer. Only the '0' codes are regulated by the feds. The third digit indicates the sub-system affected; 1 = fuel control, I don't recall what 2 is, 3 = secondary ignition/misfire, 4 = evaporative emissions, etc.. The last two digits indicat the cause of the failure, as assigned by the feds and SAE.

The main advantage is that OBDII monitors all onboard emissions systems (tailpipe, evaporative, in Standby, Key On Engine Off and Key On Engine Run) for performance as well as outright failure. The MIL (Malfunction Indicator Lamp, or Check Engine lamp) will illuminate to indicate most issues or failures. The MIL will flash if there is a failure that can cause damage to the catalytic converter.

It has been shown that subsequent generations of OBDII are so good at their job, that simply scanning for DTCs (Diagnostic Trouble Code) is better than any other test that could be performed to the vehicle.

Therefore, most states that do testing simply check for DTCs on '96 and newer vehicles, while older vehicles may still be required to be tested on a treadmill.

[getnpsi]

OBD-II has nothing but advantages. When you have a p0304 or something you know to start poking around at cylinder 4 and not have to spend 70 bucks on a whole plug and wire set...like i see all the time on older car forums. Over and over we all have seen huge lists of tuneup items and the car still runs like doodoo. There is a definate generation gap forming with mechanics both professional and recreational. Im 32 so i put myself right smack in the middle.

[lasvegascop]

So with that said when your check engine light comes on open the hood. In the engine bay, drivers side, next to the fire wall you will find a 1 pin female connector.

Pics of what that connector looks like plzzz?!?!?!?!

PS.
great info !!

[2002maniac]

^^

oops!

[BigWheel]

Pics of what that connector looks like plzzz?!?!?!?!

PS.
great info !!

I'll see if I can get a picture for you tonight.

[Levitan]

Then, after you fix the error, how do you reset the codes? Pull the battery cable? Then retest for codes?

[BigWheel]

Here is the best picture I could find. The STI is the single connector on the right.

Once you've identified the trouble codes and fixed the problem detach the negative battery cable and step on the break peddle for 5 seconds. The light will go out unless there are other codes to be pulled.

[drof 89]

Do you leave the STI connected to ground while you do the battery and brake thing? Thanks

[Levitan]

^^ Good question drof!

"Once you've identified the trouble codes and fixed the problem detach the negative battery cable and step on the break peddle for 5 seconds. The light will go out unless there are other codes to be pulled."

Also, do you detach the negative cable....Then reattach cable... then step on brake pedal for 5 seconds?