PSP Switch Signal Circuit Troubleshooting

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This signal informs the ECU when the power steering load is high. The ECU can then adjust idle speed as necessary to maintain smooth engine operation.
1. Connect system checker harness between ECU and wire harness connector.
2. Turn ignition switch to On position. On 1986-87 models, measure voltage between terminals B10 (+) and A18 (-) of checker harness. Voltage should be less than 3 volts. On 1988 models, measure voltage between terminals B12 (+) and A18 (-) of checker harness. No voltage should be measured.
3. If voltage is as specified, proceed to next step. If voltage is not as specified, proceed as follows:
a. Disconnect 2 pin connector from power steering pressure switch.
b. Connect red terminal to black terminal and measure voltage. Voltage should be approximately 10 volts. If voltage is not as specified, replace pressure switch and repeat test. If voltage is as specified, repair open in red wire between ECU and pressure switch, or repair ground connection in black wire.
4. Start engine, then turn steering wheel slowly and measure voltage between terminals B10 (+) and A18 (-) on 1986-87 models and between B12 (+) and A18 (-). Voltage should be approximately 10 volts.
5. If voltage is as specified, power steering oil pressure signal is OK. If voltage is not as specified, proceed to next step.
6. Disconnect ``B'' connector from right side wire harness. Do not disconnect connector from ECU. Voltage should be approximately 10 volts.
7. If voltage is approximately 10 volts, proceed to next step. If voltage is not as specified, substitute a good ECU and recheck voltage. If voltage is now as specified, replace ECU.
8. Reconnect ``B'' connector, then disconnect 2 pin connector from power steering pressure switch and observe voltage. If voltage is approximately 10 volts, replace pressure switch. If measured voltage is not 10 volts, repair short in red wire between ECU and pressure switch.