Self-Diagnostic Codes: Retrieval and Mysterious Meaning. -
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Unread 01-22-2009, 04:03 PM   #1
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Delta347's Avatar
1990 YJ Wrangler 
Join Date: Mar 2008
Location: Anaheim, California
Posts: 1,578
Self-Diagnostic Codes: Retrieval and Mysterious Meaning.

First Off, From What I recall, these are 1991 and later. Even though I am a 1990 I feel there are ample reasons to post this because I notice some people don't know they have this function available to them and others who do simply don't know how to retrieve the codes or how to interpret them.

The best way to tell if your Jeep is storing a code is if the "CHECK ENGINE" light comes on. (Or "POWER LOSS" as some Haynes manuals for YJs will state.)

Your Jeep.
Your Jeep's Keys.
A pen/pencil (to record codes with).
Paper (to record codes onto).

To retrieve codes (even if the light isn't on but you think something is wrong) simply:

1) Set the parking brake and put your transmission in NEUTRAL (MANUAL) or PARK (AUTOMATIC).

2) *According to Haynes Maual*: Run the engine to 2,500RPMs in the appropriate above gear. Cycle the A/C (if you still have one) briefly, then turn it off. [Automatic Only] With your foot on the brake shift into each gear position until you reach L (Low/First) then begin shifting back until you reach park.

3) Now on to actually retrieving your codes. Turn your ignition key to "ON", "OFF", "ON", "OFF", and back to "ON" and leave it there.

4) Watch the ENGINE LIGHT (or POWER LOSS light). It will blink to indicate numbers. It will 'blink to indicate the first number of the digit then pause and blink to indicate the second digit of the number'.

4 Example) 23 MAT Sensor Circuit: Check engine light would blink twice for the 2, then pause (About 2 seconds) and blink 3 times for the 3. Put the two together and you have 23.

NOTE: The pause between DIGITS OF A CODE is Approximately 2 seconds.

NOTE: The pause between CODES is Approximately 4-5 seconds. (IF Multiple Codes are being reported)

NOTE: When you receive CODE 55 it means the Diagnosis is done. No more codes will be generated until you restart the process.

Haynes Note: "Certain Criteria must be met for a fault code to be entered into the computer memory. The criteria may be a specific range of engine RPM, engine temp. or input voltage to the computer. It is possible a fault code will not be entered into memory despite a malfunction".

SELF-DIAGNOSTIC CODES (1991 and later models):
CODE: Probable Cause:

11 Ignition

13 Manifold Absolute Pressure (MAP) Sensor Vacuum

14 Manifold Absolute Pressure (MAP) Sensor Electrical

15 Distance Sensor or Circuit

17 Engine Running Too Cool

21 Oxygen Sensor or Circuit

22 Coolant Temperature Sensor or Circuit

23 MAT Sensor or Circuit

24 Throttle Position Sensor (TPS) sensor or Circuit

25 Automatic Idle Speed (AIS) Circuit

27 Fuel Injector Control

33 Air Conditioning Clutch Relay

41 Alternator Field

42 Automatic Shutdown Relay

44 Battery Temperature Sensor

46 Battery Over Voltage

47 Battery Under Voltage

51 Oxygen Sensor - lean condition indicated

52 Oxygen Sensor - rich condition indicated

53 Internal Engine Controller Fault

54 Distributor Sync Pickup

55 End of Code Output

62 Emissions Maintenance Reminder (EMR) mileage accumulator

63 Controller Failure EEPROM write denied

*Mostly Thanks To The Haynes Manual*
*If anyone knows any other codes let me know so I can list them out*

I really hope this helps some people who have been asking. I see codes every couple of days posted by users who aren't sure what they mean just that they have them so hopefully this can become some sort of reference tool, especially if one doesn't own a Haynes or Factory manual. Good Luck!

Originally Posted by Leans93 View Post
So ghost has a plug in his hole and opihi has a gaping hole, Do I need to worry about this hole at all? I just don't want to start her up and have something spewing out of it.
Side Effects may include dry mouth, nausea, vomitting, water retention, painful recolage, hallucination, dementia, psycosis, coma, death, and halitosus. YJs are not for everyone please consult your physician before use.
Delta347 is offline   Reply With Quote Quick reply to this message
Unread 03-29-2014, 11:20 AM   #2
Registered User
1995 YJ Wrangler 
Join Date: Mar 2014
Location: logansport, in
Posts: 16
nice! Thanks
happyhollowhors is offline   Reply With Quote Quick reply to this message

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