Ford OBD-I Self Tests and Code Reading


1986 F150 5.0 (302) EFI
There are quite a few web sites that give info on how to get the codes manually with jumper (flash method) or with a code reader. However most of them do not give much detail as to how it's done and what to expect.    Jumper this .. read your codes.  The code reading process can be kinda confusing if you have never done it before. But it's not really very hard to do.
Below I give some details on how the OBD-1 codes are read. I show how codes are read with a simple jumper / test light and with a code reader.


OBD-I Connector



Connector location


Code Reading Options:

There are several ways of ways to get the codes displayed.
Note: Not all vehicles have the flashing CEL function.  My truck has the dash light but I found the socket pulled out and tucked away behind the dash. I put a bulb in it and put it back where it should go but I have never seen the light come on ever. Does not come on even when the ignition is started like the other lights. I also find no CEL light wiring in the diagrams and no mention of it in any text in the shop manual.


Manual Jumper Method:


Tools Needed
  1. Pen and notepad
  2. ~ 4" jumper wire with spade lugs at each end.
  3. Automotive Test Light
    (or any 12V bulb with wires attached)
  4. Straight wire with one spade lug
  5. Jumper with 'alligator' clips both ends
Notes:
  • I filed the edges of the spade lugs so they
    would fit better in the socket.
  • Items 3, 4, 5 are not required if you have
    a functioning CEL on your dash panel.


Tools


Jumper and Test Light Connection
Jumper test light
Connect a jumper wire between the single pin connector and pin 2 of the 6 pin connector:  If you have a working CEL then this is all that is required.                 
               Test light connects between pin 4 and positive terminal of the battery

Note if you have the older MCU system ('81 to about '84) with only one 6 pin connector then the jumper goes between pin 2 and pin 5 (directly below pin 2). The test light is connected the same.  Consult the Equus code reader manual for more setup information. You can download the manual from the link at the end of this page.




Complete Setup with Test Light

Lit
Here is an automotive test light connected to the output (pin 4) of the test connector. I used the yellow clip lead to connect the test light to the wire on pin 4.
The test light is clamped to the +12V terminal on the starter solenoid or battery.
The light positioned as shown here can be seen from inside the cab looking under the open hood. Helpful when doing the tests with only one person as the test operator needs to be in the drivers seat.

Skip code reader section and go to reading flash codes

Code Reader Method:

Types of OBD-I Code Readers:

The most basic code tool just has a flashing light and/or audio tone generator. Not much different than the CEL or test light method.
A better reader has a digital display readout of the codes.
Early Ford models up to '91 use 2 digit codes. '92-'95 Ford went to 3 digit codes. All '96+ are OBD-II.

Note that OBD-I  system used in vehicles from '81 to about '95 are not universal between manufactures like OBD-II. There are different versions for Ford, GM, and foreign makes. Different connectors, different codes etc. Be sure to get a unit that can do Ford vehicles.
Also OBD-I systems give no 'live' data. Only tests and codes. So you will not find any readers with USB or serial computer connections. There is no point.

Most OBD-II code readers for modern vehicles will not read OBD-I codes! (unless you get a fairly expensive unit that can read both types).

I ended up with this unit:
EQUUS 3145 or INNOVA 3145. About $25.00 on Amazon

3145


6' Extension cable model EPI3149. Also about $25.00
The cable is a bit expensive for what it is. A cable could be made for a few $ in parts


Direct to Port With Extension cable
               The 3145 reader shown directly attached to the port connectors. 
                With extension cable, reader can be operated inside the cab.

                                             
The optional extension cable is really handy and almost essential for 1 person operation especially when doing the interactive part of the self tests.


The EQUUS 3143 is the non digital version $10.99 on Amazon. The extension cable works with this one as well.
The 3143 appears to be discontinued by the manufacture but is still available at some stores like Amazon.

3143
               EQUUS 3143


Reading Flash Codes:
This sequence would give codes 32 & 21
 Flash
    1

 Flash
    2

Flash
   3

 2 sec

Flash
  1

Flash
  2

     4 sec   

Flash
   1

Flash
  2

 2 sec
Flash
   1
 etc
                   


Ford OBD-I  Self Tests and Codes:

Codes are generated by the vehicles computer system for current problems and will make the Check Engine Light or CEL come on if equipped.
Also previously generated codes for intermittent problems or problems that have gone away are stored as well.

The intermittent codes will eventually be deleted after so many start up cycles.
-OR-
All codes are cleared by removing the battery cable.
    Note: Not all vehicles have a CEL but codes are stored just the same.
    Any CEL codes stored in memory are retrieved as part of the KOEO self test procures described below.
    Note you can not get any codes without first running the KOEO test.

    The code reader or manual jumper method is used to start a series of self tests. The self tests themselves will generate pass fail codes when run.
    There are 2 levels of self tests.
    Codes produced by the self test process itself are NOT stored in the vehicle memory.


    KOEO Tests: (Key On - Engine Off)


    Code Reader Method:
    1. Turn ignition key OFF
    2. Install code reader on OBD-I connectors.
    3. Turn ignition to ON
    4. Turn code reader on and press test button on code reader
    Jumper Method:
    1. Turn ignition off.
    2. Install test light if you don't have a CEL.
    3. Install jumper.
    4. When ready turn ignition on.
    The tests begin as soon as the key is turned on if you use the jumper method and when you push the test button if using the code reader. You will hear relays clicking both in the engine bay and inside behind the dash.
    The engine MUST be warmed up before doing the tests
    .
    KOEO Sequence and Timing (Time is approximate)

     KOEO  Tests

     -Pause- 

     KOEO  Codes

     
    Repeat KOEO codes

     -Pause-
    Separation code
    10

     -Pause-
       CEL
     codes

    Repeat CEL codes
    5-6 sec
    9-10 sec
    Varies

    Varies
    6-9 sec
    -
    6-9 sec
    Varies

    Varies

    Note the pass code is 11 or 111 for both the KOEO test and the stored (CEL) codes. So a passing code dump would look like this::
    ......11....11........10........11.....11....       or for later models   111.....111....... 10........ 111.......111...

    This would be passing sequence - flash method:  (11,11,10,11,11)
    Flash
    2 sec
    Flash
      4 sec 
    Flash
    2 sec
    Flash
         9 sec   
    Flash
    2 sec
    ----
         9 sec   
    Flash
    2 sec
    Flash
      4 sec 
    Flash
    2 sec
    Flash

    When retrieving codes from the code readers memory, the repeated codes are not shown so you would get:
    11...10...11     or      111....10.....111

    Here is an example of code output when the engine was not warmed up enough.
    .......21.....24......21....24.....10.......11.......

    Code reader output of above:
     ......21...24.....10.....11....

    Note the 21 and 24 codes are related to coolant and air temperature sensors.


    NOTE: You need to fix the problems indicated in the above KOEO tests BEFORE going on to the KOER tests below.  You can do the KOER tests just to see whats up but fix the KOEO codes first before attempting to fix anything indicated in the KOER tests. You may or may not have the same codes later after you fix the KOEO problems. If you have passing KOEO tests but still have CEL or memory codes then do go on to the next tests.



    KOER Tests:  (Key On - Engine Running)
    There are some user interactions required with this test. ie turn the steering wheel, step on the brake, and press the accelerator to WOT at the proper time.
    If not done properly you will get various failure codes. 25 and 77 for no WOT etc.

    Code Reader Method:
    1. Turn ignition key OFF
    2. Install code reader on OBD-I connectors.
    3. Start engine
    4. Turn code reader on and press test button on code reader
    Jumper Method:
    1. Turn ignition key off
    2. Connect a test light if you do not have a CEL.
    3. Install jumper (Jumper can be installed after engine is running)
    4. When ready start the engine.
     
    KOER- Start to end is about 2.5 minutes depending on how many codes are output.

    KOER Sequence and Timing  (Time is approximate )
      # Cyl +
    Do brake &
     PS Test
     KOER Tests

     10 
    Do WOT test

     10 

     -Pause-
     KOER Codes
    Repeat KOER Codes
    10 sec
    45 Sec
    -
    10 Sec
    -
    4 sec
    Varies

     Varies

    (4 flashes = 8 Cyl, 3 flashes = 6 Cyl)

    Examples with code reader - all good - no codes (8 cyl engine):
    Note that the code reader will automatially convert the cyl code into an 8 or 6.
    8....  10........10 ..11...11

    Viewing code reader memory would be:
    8....11..

    Example when the user did not do the WOT test.....
    8......10......10.....25....77....25....77......

    When reviewing from the code reader memory the code would look like this:
    8...25...77....
    (25= Knock sensor, 77 = Operator error WOT not done)


    Repeating Tests:

    If you want to repeat either the KOEO or KOER tests from the beginning you must turn the ignition off and back on. Also turn the code reader off and back on.


    Clearing Codes:
     
    If you want to clear all codes then remove the (-) battery cable for a few minutes.

    Codes are cleared on the code reader by restarting a test or removing the batteries from the tester.



    Code List:
    Note that many code lists found on the internet are not complete, or are abbreviated.  For example MANY codes have different meanings depending on whether it's a car or truck. The Equus 3145 manual has a complete code list.

    Download the EQUUS 3145 manual

    Hint for codes only, open the PDF and print out pages 49-67.

    Before replacing parts which may be indicated by the codes first check, connectors, wiring, vacuum lines etc. The system has no way to distinguish the difference between a bad part and bad wiring to/from the part.

    Back to top


    Last updated 3/26/12

    Questions or comments email here