Reading CEL Codes

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Workman1788

Registered
I have a CEL that randomly comes on in my '95 mark. Unfortunately, I only have a scanner for OBDII. Is it possible to do a KOEO self-test on this car? Some fords allow you to use a jumper wire in the diagnostic port and turn the key on to make the CEL flash, can that be done. If so, what pins need jumped and does anyone have a list of codes?
 
You can do that or you can get the 12 dollar code reader too. :) Let me look up the pins.
 
IMPORTANT NOTES


Ignition key MUST be cycled "OFF" for 10 seconds prior to the start of any KOEO or KOER self-test. If the key is not cycled off the system will not reset and the next test will not initiate correctly.
Correct results of the quick tests are dependent on the proper operation of related non-EEC-IV components.
Minor deviations from this procedure or the Flow of Diagnosis may cause false codes to be output.
KEY ON ENGINE OFF (KOEO) SELF-TEST PROCEDURE


Start engine and bring to normal operating temperature. If engine will not start or stalls after starting, proceed with next step.
Turn the key "OFF", then wait ten seconds.
Data Link Connector (DLC)
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Analog Voltmeter Connection
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Activate the self test by grounding the Self-Test Input (STI) connector.
Turn the ignition key "ON".
Key On Engine OFF (KOEO) Diagnostic Trouble Code Format
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Record all codes received.
Turn ignition "OFF".

RESULTS, WHERE TO GO NEXT


Record all codes received:
Distinguish between ON DEMAND (hard) codes and CONTINUOUS MEMORY codes. On Demand codes are output first, followed by, a separator pulse, followed by Continuous Memory codes.
Record the order in which they were received.
If a pass code (111) is received for ON DEMAND (hard) codes, proceed to Timing Checks. See: Base Ignition Timing Check
If any ON DEMAND (hard) codes are received, refer to Diagnostic Trouble Code Diagnostic Charts for appropriate testing procedures. See: Pinpoint Tests
NOTE: ON DEMAND (hard) codes should be diagnosed in the order they were received.



Continuous memory codes recorded in this step will be used for diagnosis after ALL ON DEMAND (hard) codes from BOTH the KOEO and the KOER test have been corrected.
 
Thank you much. I'm pretty sure it's just in need of plugs and wires but I just want to be sure that there aren't any major issues.
 
If you get some crazy code you're unsure of, post it here and we'll help you out.
 
Ok, the car is showing a 543 and 524. With a little google search, I've come up with this...

"524 + 543 - Continuous Memory DTCs 524/543 indicate that sometime during vehicle operation, when the PCM commanded the fuel pump on, voltage was not detected on the power-to-pump circuit (through FPM, PCM Pin 8). Although DTC 524 refers to the low speed output (VCRM Pin 24) and DTC 543 refers to the high speed output, it is not possible to distinguish between circuits due to the vehicle wiring and fuel pump operating strategy."

The problem with the car is this, once warm it develops a misfire and has a lot of trouble accelerating. If I give it about 3/4 throttle or more, it springs back to life as if nothing was wrong. The plugs have been changed by the previous owner but the wires look to be original.
 
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Well...sounds to me like you have two problems.

First being super old plug wires. Lets say best case scenario you only have 10k miles on your 95, the wires are still 15 years old.

Your symptoms indicate to me that one or more of your wires are finding a ground or has a crack in the electrode under normal load conditions causing a misfire but when you go 3/4 + throttle, you're demanding more spark from the coils, allowing the spark to pass completely through the wires without grounding out.

The 524/543/556 code is a intermittant issue caused by one of these...

Possible causes:

Open in power-to-pump circuit between the VCRM and FPM splice.
Open in B(+) supply to VCRM (Pins 4 and 5).
Left Heated Oxygen Sensor (HO2S) short to power.

My suggestion is to start with the general maintanence and then tackle the intermittant issues.
 
Hopefully I'll be able to get the plugs and wires this weekend. May throw a fuel filter on as well. While driving home tonight, it was trying to bog down on me and it one point it popped a little through the intake.
 
Definitely a spark issue. Wouldn't back fire if you had a loss of fuel. The less you drive it the better....
 
I was thinking it could be an o2 sensor as well. We'll see what she does after a weekend of good maintenance. Hopefully it will pur like a... well a Lincoln.
 
Plugs and wires weren't the whole issue but I lucked out and fixed it for free. The bolt going into the throttle body to hold the air intake on was broken off.
 
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