Notes On Fault Tree
NOTE:
The following step numbers refer to circled numbers on diagnostic chart. For diagnostic flow chart refer to ECM DTC EO23: EST CIRCUIT PROBLEM
. See FigureFigure
. For circuit identification, see Fig 1
.
- Four jumper wires must be obtained for use in the diagnostic procedure. The jumpers should be about 12 inches long with a male and female weatherpack connector on either end (P/N 12014836 and 12014837). With the distributor connector disconnected, use the jumpers to reconnect the terminals per instructions provided on the code EO23 chart.
- With only Distributor Reference and Distributor Reference Ground jumpered, engine will run at backup spark. Checking for proper ground connection between ECM and the engine and the ECM and HEI.
- Checking for ECM providing an EST output on circuit 423.
- Checking for HEI module able to ground EST signal with open Bypass Circuit.
- Checking for HEI module able to recognize a voltage on the Bypass circuit and to stop grounding EST (ECM controlling timing).
- Checking for Bypass signal to the module. If Bypass is being sent by the ECM to the HEI and if the module is interpreting Bypass voltage correctly, then the module will switch off the ground to the EST.
- If the chart leads to "EST Circuit Is OK" then a fault may exist in the 6-way weatherpack connector. Check for proper connector mating and for pins backing out of the weatherpack. If no trouble is found with the connector, reconnect the 6-way, clear codes and retest.