Truckertom21

its a 1991 XJ with the 4.0 HO auto Laredo 4 door and 4X4

5-90

Chrysler OBD-I. The TCU should still be separate, and mounted behind the right-hand IP panel lower trim fascia. The ECU is probably underhood, a largish black box with a large harness connector plugged into it.

You can use an OBD-I code reader to interrogate the thing, or you can get codes to flash using the CEL/MIL on the dash by turning the key (starting in the OFF position): OFF-ON-OFF-ON-OFF-ON in the space of three seconds. Do not start the vehicle.

The CEL/MIL will then flash in a pattern. Rapid flashes are counted for a single digit, with a longer pause in between digits. I believe the code sequence will repeat three times, and each code is two digits (codes are listed on my site.)

Using a single dash for a "short pause" and three dashes for a "long pause," DTC code 43 would look like: FLASH-FLASH-FLASH-FLASH---FLASH-FLASH-FLASH.

If you pull codes, you can refer to my site first (I collected them from FSMs) before you start pillaging around and asking questions. The DTC listings for OBD-I and OBD-II Jeeps are in the Technical section.

CEL = Check Engine Lamp
DTC = Diagnostic Trouble Code
ECU = Engine Control Unit
IP = Instrument Panel (dashboard)
MIL = Maintenance Indicator Lamp
OBD = OnBoard Diagnostics
TCU = Transmission Control Unit

Truckertom21

okay thanks, when i last drove it the check engine light came one but only on my return trip i think i already know what the problem is but im gonna get the code reader to make sure. the reader im thinking of has a book that will tell me what the code is in plan english


also this may be a dumb question but what dose DTC mean?

ol"blue

Diagnostic Trouble Code.