This page is dedicated to Ford PCM codes prior to OBD II, the codes in this particular system  can be retreived with an analog voltmeter, before connecting the volt meter warm up the engine to its normal operating  temperature, place it in park if it has an automatic transmission or in neutral if it has a manual transmission, make sure that the parking brake is set and turn the engine off for about 10 seconds.

Locate the diagnostic test connector under the hood, install the positive voltmeter lead to the positive battery cable, and the negative voltmeter lead to the pin number 4 ( STO ) on the test connector. Install a jumper wire from the test terminal( single wire that usually has a gray plastic connector and is attached to the diagnostic test terminal) to pin number 2 of the Diagnostic test terminal ( STI ).

Turn the ignition key on ( engine not running ) and observe the needle sweeps on the analog voltmeter, by counting the needle sweeps you will be able to determine the codes, for example: a code 25 will be displayed as follows: the voltmeter will sweep once, pause for 1/2 second and sweep again ( indicating the first digit of the code " number 2"), followed by a 2 second pause the needle will sweep 5 times ( indicating the second digit of the code " number 5" ).
On 3 digit codes the sequence is the same except there will be an additional sequence of sweeps to indicate the third digit in the code.

If there are 2 or more codes stored in the computer, they will be separated by a 4 second pause between sweeps.

You can also perform a test with the engine running on this system, but we recommend using a scan tool to get an accurate reading if you decide to do a running test, we won't list the codes related to the engine running test to avoid confusing you.

2 Digit trouble codes

CODE     PROBABLE CAUSE

11   System pass
13   D.C. motor doesn't move ( 1987-1990 1.9L CFI and 2.3L CFI )
13   D.C. motor doesn't follow dashpot ( 1987-1990 1.9L CFI and 2.3L CFI )
14   PIP circuit failure
15   EEC read only memory ( ROM ) failed, or keep alive memory ( KAM ) in continuous
15   EEC keep alive memory ( KAM ) failed ( 1990 )
16   Ignition diagnostic module ( IDM ) signal not received ( 1990 and 1991 3.0L 1991 4.0L truck)
18   Loss of TACH input to ECA Spout, circuit grounded ( 1984 on )
18   SPOUT circuit open ( 1987 on )
19   Failure in EEC reference voltage circuit ( 1986-1989, except 1.9L, 2.3L, 3.0L MA and 3.8L SC )
19   CID circuit failure DIS ( 1989-1991 3.0L MA, 3.8L SC and 4.0L)
21   ECT out of range during self test
22   MAP/BP sensor out of range during self test ( through 1991)
23   TP sensor out of range during self test
24   VAT sensor out of range during self test ( 1.6L PFI and 2.3L turbo )
24   ACT sensor out of range during self test ( except 1.6L PFI, 1.9L PFI and 2.3L turbo )
26   VAF sensor out of range during self test ( 1.6L PFI, 1.9L PFI and 2.3L Turbo, through 1990 )
26   MAF/VAF sensor out of range during self test ( 1988 1.9L PFI, 2.3L Turbo and 5.0L PFI )
26   MAF sensor out of range during self test ( 1989-1991 2.3L PFI, 2.9L PFI, 3.0L SHO, 3.8L SC, 4.0L SEFI and
          5.0L SEFI )
26   TOT sensor out of range during self test ( 1989 and later 5.8L, 7.3L diesel and 7.5L trucks with E4OD )
27   Insufficient input from vehicle speed sensor ( 1987-1989 2.3L turbo )
28   Intake air temperature at VAF meter out of range during self test
28   Loss of ( right ) primary TACH ( 1989 and 1990 dual plug DIS )
31   EVP voltage out of range during self test ( 1983, 1991 and 1992 2.3L OHC and 3.8L CFI )
31   PFE/EPT/EVP below minimum voltage ( 1987-1990 and 1993 )
32   EGR valve not seated ( 1991 1.9L, 2.3L HSC and 3.0L SHO )
32   EGR/EVP closed voltage too low ( 1991 on )
33   EGV valve not seated ( 1983-1989 1.9L CFI, 2.3L OHC, 3.0L and 3.8L SFI )
33   EGR valve not opening, or opening not detected  ( 1985-1990 PFE and Sonic )
33   Insufficient EGR flow detected ( 191 on PFE and Sonic )
33   Throttle position noise ( 1993 7.3L diesel )
34   Defective PFI/EPT sensor ( 1985-1989 1.9L CFI, 2.9L and 3.0L )
34   Exhaust pressure high or defective PFE/EPT sensor ( 1985-1991 )
34   EVP voltage above closed limit ( 1986-1990 )
35   PFE/EPT/EVP circuit above maximum voltage ( 1985 on )
38   ITS circuit open ( 1987-1990 1.9L CFI, 2.3L CFI and 2.5L CFI )
39   Automatic transaxle lock-up circuit failed ( 1986-1990 3.0L cars)
41   EGO sensor indicates system lean ( 1983-1990)
41   No EGO sensor switching detected ( 1987-1990 )
42   EGO sensor indicates system rich ( 1983-1990 )
42   No EGO sensor switching detected ( 1987-1990 )
43   EGO lean at wide open throttle ( 1987-1990 1.9L PFI and 2.3L Turbo )
51   ECT sensor circuit open or ECT indicates -40 degrees F ( through 1991 )
52   Power steering pressure switch open ( 1985 on )
53   TP sensor circuit open ( 1983 ) or above maximum voltage ( 1984 on )
54   VAT sensor circuit open ( 1985 and 1986 1.6L PFI, 1.9L PFI and 2.3L turbo )
54   ACT sensor circuit open or ACT indicates -40 degrees F ( 1985-1991, except 1.6L pfi, 1.9L PFI and 2.3L turbo )
55   Key power circuit low ( 1985 through 1990 1.9L CFI, 2.3 L CFI and 2.5L CFI )
56   MAF/VAF circuit above maximum voltage ( 1983-1990 1.6L PFI, 1.9L PFI, 2.3L turbo, 3.0L SHO, 3.8L SC and 5.0L PFI )
56   TOT sensor circuit open or -40 degrees F. indicated by TOT ( 1989 on with transmission oil temperature sensor )
57   NPS circuit failed open ( 1986-1990 3.0L car )
58   ITS circuit open ( 1987-1990 1.9L CFI, 2.3L CFI and 2.5L CFI )
58   VAT sensor circuit open  or -40 degrees F indicated by VAT ( 1987-1990 1.9L CFI )
58   Crank fuel delay service pin in use or circuit grounded  ( 1990 2.9L )
59   Automatic transaxle 4/3 circuit failed open ( 1986-1990 3.0L and 3.8L )
59   2/3 shift error (1991 on 7.3L diesel, 5.8L and 7.5L with E4OD )
59   AXOD 4/3 circuit failed closed
61   ECT sensor circuit grounded or below minimum voltage
62   Automatic transaxle 3/2 or 4/3 circuit grounded ( 1986-1990 3.0L )
62   Converter clutch error ( 1989-1991 5.8L, 7.3L diesel and 7.5L with E4OD )
63   TP sensor circuit below minimum voltage ( through 1991 )
63   Fuel injector pump lever circuit below minimum voltage ( 1989-1991 7.3L diesel with E4OD )