ECM Codes - Procedure Correction
91isuzu02
BULLETIN NUMBER SB91-03-004
ISSUE DATE March 7, 1991
GROUP EMISSIONS
RODEO (UC) CLEARING ECM CODES
AFFECTED VEHICLES
All Rodeo (UC) models with V6 engine.
SERVICE INFORMATION
ECM code-clearing procedures and ECM fuse identification are incorrectly specified in the following Workshop Manual:
Manual Page No.
1991 Rodeo (UC) 6E2-5,
(Publication No. AIMI-SVC-195, 6E2-A-4
part No. 2-90991-072-0) 8-21
This Service Bulletin contains corrected ECM fuse identification and ECM code-clearing procedures.
DRIVEABILITY AND EMISSIONS - FUEL INJECTION 3.1L VIN D 6E2-5
Intermittent "Check Engine" Light
In the case of an "intermittent" problem, the "Check Engine" light will light for ten (10) seconds and then will go out. However, the corresponding trouble code will be stored in the memory of the ECM until the battery voltage to the ECM has been removed. When unexpected codes appear during the code reading process, one can assume that these codes were set by an intermittent malfunction and could be helpful in diagnosing the system. An intermittent code may or may not re-set. If it is an intermittent failure, a Diagnostic Trouble Code Chart is not used. Consult the "Diagnostic Aids" on the page facing the diagnostic chart corresponding to the intermittent trouble code. Section "B" also covers the topic of "Intermittents." A physical inspection of the applicable sub-system most often will resolve the problem.
Reading Codes
The provision for communicating with the ECM is the Assembly Line Diagnostic Link (ALDL) connector (See Figure A-4). The ALDL is usually located in the center console and is sometimes covered by a plastic cover labeled "DIAGNOSTIC CONNECTOR." It is used in the assembly plant to receive information in checking that the engine is operating properly before it leaves the plant. The code(s) stored in the ECM's memory can be read either through a hand-held diagnostic scanner plugged into the ALDL connector or by counting the number of flashes of the "Check Engine" light when the diagnostic terminal of the ALDL connector is grounded. The ALDL connector terminal "B" (diagnostic terminal) is the second terminal from the right of the ALDL connector's top row. The terminal is most easily grounded by connecting it to terminal "A" (internal ECM ground), the terminal to the right of terminal "B" on the top row of the ALDL connector. Once terminals "A" and "B" have been connected, the ignition switch must be moved to the "ON" position, with the engine not running. At this point, the "Check Engine" light should flash Code 12 three times consecutively. This would be the following nash sequence: "flash, pause, flash-flash, long pause, flash, pause, flash-flash, long pause, flash, pause, flash-flash." Code 12 indicates that the ECM's diagnostic system is operating. If Code 12 is not indicated, a problem is present within the diagnostic system itself, and should be addressed by consulting the appropriate diagnostic chart in Section "A".
Following the output of Code 12, the "Check Engine" light will indicate a diagnostic trouble code three times if a code is present, or it will simply continue to output Code 12. If more than one diagnostic trouble code has been stored in the ECM's memory, the codes will be output from the lowest to the highest, with each code being displayed three times.
Clearing Codes
When the ECM sets a trouble code, the "Check Engine" light will come "ON" and a trouble code will be stored in metnory. If the problem is intermittent, the light will go out after 10 seconds, when the fault goes away. However, the trouble code will stay in the ECM memory until the battery voltage to tbe ECM is removed. To clear all stored trouble codes, remove fuse # 3 from the driver side fuse box for 30 seconds. Trouble Codes should be cleared after repairs have been completed. Also, some Diagnostic Charts will tell you to clear the codes before using the chart. This allows the ECM to set the code while going through the chart, which will help to find the cause of the problem more quickly.
CAUTION:
To prevent ECM damage, the key must be "OFF" when disconnecting or reconnecting power to the ECM (for example battery cable, ECM fuse, jumper cables etc.)
Diagnostic Mode
When the Diagnostic terminal is grounded with the ignition "ON" and the engine "OFF," the system will enter what is called the Diagnostic Mode. In this mode the ECM will:
1. Display a Code 12 by flashing the "Check Engine" light (indicating the system is operating correctly).
2. Display any stored trouble codes by flashing the "Check Engine" light. Each code will be flashed three times, then Code 12 will be flashed again.
3. Energize all ECM controlled relays and solenoids except fuel pump relay. This allows checking circuits which may be difficult to energize without driving the vehicle and being under particular operating conditions.
4. The IAC valve moves to its fully extended position on most models, blocking the idle air passage. This is useful in checking the minimum idle speed.
Figure A-3 - ECM Wiring Diagram 3.1L (2 of 3):
6E2-A-4 3.1L (VIN D) DRIVEABILITY AND EMISSIONS
Fig. 8-45:
FUSE BLOCK CIRCUIT - V6.3.1L