Actron 9640 user manual Code Lookup, Print Data, Koer Procedure

GM Historic (OBD I) Diagnostics

KOER Procedure

With the engine running, the Field Service mode can be used to measure base timing, check open loop/closed loop operation, and determine if the engine is running rich or lean.

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1) Engage parking brake and block drive wheels.

2) Verify engine is cold. If engine is hot or warm, allow it to cool.

3) On scan tool, place Field Service On.

4) Start engine and place transmission in Park or Neutral. The Check Engine light will flash once.

5) Warm the engine by idling for 2 minutes at 2000 RPM.

6) Observe Check Engine light.

• If Check Engine light flashes 2.5 times a second, the on-board computer is operating in Open Loop.

• When the engine warms up to normal operating temperature, the on-board computer is now operating in Closed Loop. The Check Engine light should flash once a second. The on-board computer is now operating in Closed Loop.

• If Check Engine light...

— flashes equally ON/OFF, then the fuel system is running normally.

— is mostly ON, then the fuel system is running Rich.

— is mostly OFF, then the fuel system is running Lean.

7) On some engines, the spark advance timing is fixed during Field Service Mode. This allows the technician to measure the engine base timing.

Code Lookup

Refer to “Code Lookup” on page 4-22 of Global OBDII Diagnostics.

✓Enter only the code numbers. No system designation is used for historic DTCs, they are either History or Current codes.

✓A “P” appears at the beginning of the DTC if the vehicle uses OBD II type codes.

Print Data

Refer to “Print Data” on page 4-20 of Global OBDII Diagnostics.

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