S15/T15 2WD Jimmy V6-262 4.3L (1991)
ABS Light: Description and Operation
Antilock Light Circuit
The 4WAL ECU uses an amber-colored "Antilock" warning light to alert the driver of a malfunction it has detected. The ECU completes the "Antilock"
light circuit through the 10-way connector terminals B and J.
The ECU completes the circuit for the "Antilock" light by providing a ground. It operates the light by making it do one of two things:
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Light steadily during an initial test at the beginning of an ignition cycle, when a system malfunction exists.
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Flash ON and OFF (to present trouble code information) when a service technician grounds the ALDL diagnostic request terminal H to A.
An input monitor circuit within the ECU allows it to detect an open or shorted circuit for the "Antilock" light during the initial test for each ignition
cycle:
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When the "Antilock" light is unlit, the voltage at the monitoring point within the ECU will be high.
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The voltage at the monitor point will be low when the ECU grounds the "Antilock" light circuit.
If the ECU monitors low voltage at terminal B before it attempts to ground the light circuit, it determines that a short or open circuit exists. If the ECU
monitors high voltage after it attempts to ground the "Antilock" light circuit, it determines that a short to voltage condition exists.
In the case of either malfunction, the ECU will take diagnostic action by:
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Completing the "Brake" light to alert the driver
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Storing a trouble Code 86 (short)
