Diagnostic Procedure

Refer to ENTERING ON-BOARD DIAGNOSTICS to retrieve fault codes. When using check engine light to retrieve fault codes, refer to description of DRB-II display under FAULT CODES for an explanation of fault code. Once description of fault code is obtained, refer to appropriate trouble shooting chart to diagnose problem. Use trouble shooting chart titles to find appropriate chart.

If no fault codes are present, but vehicle still displays one of the following conditions, go to appropriate test.

• No start condition. Go to NS-1.
• Cold driveability problem. Go to DR-1.
• Warm driveability problem. Go to DR-1.
• Check engine light is illuminated. Go to DR-1.
• Charging system problem. Go to CH-1.
• Speed control system problem. Go to SP-1.

Before proceeding with diagnosis, the following precautions must be followed:

• Vehicle must have a fully charged battery.
• When performing a cold driveability test, engine must not have been started for at least 7 hours.
• When performing a warm driveability test, engine must be at normal operating temperature.
• When probing SMEC connectors, probe connectors from pin side. DO NOT backprobe connectors.
• When performing electrical tests, be careful to not cause any short circuits. This will set more fault codes, making diagnosis of original problem more difficult.
• DO NOT use a test light in place of a voltmeter.
• When checking for spark, ensure coil wire is no more than 1/4" from ground. If wire is farther away from ground, damage to SMEC may result.
• DO NOT prolong testing of fuel injectors as engine may hydrostatically lock.
• Always repair lowest fault number (check engine light) or first fault displayed (DRB-II), first.
• Always perform indicated verification test after repairs are made.