Jeep Wagoneer/Commando/Cherokee 1984-1998

Reading Codes

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CARBURETED ENGINES



When a jumper wire is connected between the trouble code test terminals 6 and 7 of the 15-terminal diagnostic connector (D2), the CHECK ENGINE light will flash a trouble code or codes that indicate a problem area. For a bulb and system check, the CHECK ENGINE light will illuminate when the ignition switch is ON and the engine not started. If the test terminals are then grounded, the light will flash a code 12 that indicates the self-diagnostic system is operational. A code 12 consists of one flash, followed by a short pause, then two more flashes in quick succession. After a longer pause, the code will repeat two more times. If more than one trouble code is stored, each will be flashed three more times in numerical order, from the lowest to the highest numbered code.

Remember that the fault message identifies a circuit problem, not a component.

FUEL INJECTED ENGINES



Entering the self-diagnostic system on models prior to 1991 requires the use of a special adapter that connects with the Diagnostic Readout Box II (DRB-II). These systems require the adapter because all of the system diagnosis is done Off-Board instead of On-Board like most vehicles. The adapter, which is a computer module itself, measures signals at the diagnostic connector and converts the signals into a form which the DRB-II can use to perform tests. The MIL or a scan tool can be used to read codes.

Remember that the fault message identifies a circuit problem, not a component.

MIL Method

This procedure may be used on 1991-96 models.

  1. Start the engine, if possible, cycle the transmission selector and the A/C switch if applicable. Shut off the engine.
  2.  
  3. Turn the ignition switch ON-OFF, ON-OFF, ON-OFF, ON within 5 seconds.
  4.  
  5. Observe the MIL on the instrument panel.
  6.  
  7. Just after the last ON cycle, MIL will begin flashing the stored codes.
  8.  
  9. The codes are transmitted as two digit flashes. For example Code 21 will be displayed as a FLASH FLASH pause FLASH.
  10.  
  11. Be ready to write down the codes as they appear; the only way to repeat the codes is to start over at the beginning.
  12.  

Scan Tool Method

See Figures 1 and 2



Click image to see an enlarged view

Fig. Fig. 1: Plug the scan tool into the data link connector-location on the left side of the engine compartment of 1992 Jeep shown



Click image to see an enlarged view

Fig. Fig. 2: Using the scan tool to diagnose a problem-coolant temp sensor reading shown

The scan tool is the preferred choice for fault recovery and system diagnosis. Some hints on using the DRB include:



To use the HELP screen, press and hold F3 at any time.
 
To restart the DRB-II at any time, hold the MODE button and press ATM at the same time.
 
Pressing the up or down arrows will move forward or backward one item within a menu.
 
To select an item, either press the number of the item or move the cursor arrow to the selection, then press ENTER.
 
To return to the previous display (screen), press ATM.
 
Some test screens display multiple items. To view only one, move the cursor arrow to the desired item, then press ENTER.
 

To read stored faults with the DRB:

  1. With the ignition switch OFF , connect the tool to the diagnostic connector near the engine controller under the hood. Turn the ignition ON .
  2.  
  3. Start the engine if possible. Cycle the transmission from P to a forward gear, then back to P , Cycle the air conditioning on and off. Turn the ignition switch OFF .
  4.  
  5. Turn the ignition switch ON but do not start the engine. The DRB-II will begin its power-up sequence; do not touch any keys on the scan tool during this sequence.
  6.  
  7. Reading faults must be selected from the FUEL/IGN MENU. To reach this menu on the DRB-II:
    1. When the initial menu is displayed after the power-up sequence, use the down arrow to display choice 4) SELECT SYSTEM and select this choice.
    2.  
    3. Once on the -SELECT SYSTEM- screen, choose 1) ENGINE. This will enter the engine diagnostics section of the program.
    4.  
    5. The screen will momentarily display the engine family and SBEC identification numbers. After a few seconds the screen displays the choices 1) With A/C and 2) Without A/C. Select and enter the correct choice for the vehicle.
    6.  
    7. When the -ENGINE SYSTEM- screen appears, select 1) FUEL/IGNITION from the menu.
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    9. On the next screen, select 2) READ FAULTS
    10.  

  8.  
  9. If any faults are stored, the display will show how many are stored (1 of 4 faults, etc.) and issue a text description of the problem, such as COOLANT SENSOR VOLTAGE TOO LOW. The last line of the display shows the number of engine starts since the code was set. If the number displayed is 0 starts, this indicates a hard or current fault. Faults are displayed in reverse order of occurrence; the first fault shown is the most current and the last fault shown is the oldest.
  10.  
  11. Press the down arrow to read each fault after the first. Record the screen data carefully for easy reference.
  12.  
  13. If no faults are stored in the controller, the display will state NO FAULTS DETECTED and show the number of starts since the system memory was last erased.
  14.  
  15. After all faults have been read and recorded, press ATM.
  16.  

 
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