DTC B1423/23: PRESSURE SWITCH CIRCUIT Lexus RX I

1. Remove ECM, located behind passenger side kick panel. Leave harness connectors attached. Connect manifold gauge set to A/C system service valves. Turn ignition on.
2. Measure voltage (backprobe) between ECM connector (E9 on 2000; E6 on 2001) terminal No. 2 (Red/Yellow wire) and ground. (Scheme 37)or (Scheme 38).
3. Start and operate engine at 1500 RPM. Press A/C button to ON position. As low-side pressure increases to more than 33.6 psi (2.4 kg/cm 2 ), voltage will change to zero. As low-side pressure decreases to less than 28.4 psi (2.0 kg/cm 2 ), voltage will change to battery voltage.
4. As high-side pressure increases to more than 455.4 psi (32.0 kg/cm 2 ) voltage will change to zero volts. As high-side pressure decreases to less than 369.8 psi (26.0 kg/cm 2 ) voltage will change to battery voltage. If voltage does not change as specified, go to next step. If voltage changes as specified, no problem is indicated at this time.
5. If voltage is not as specified, test pressure switch. See «PRESSURE SWITCH»(ref-98896-S30356855592001060500000) under COMPONENT TESTS. If switch is okay, go to next step. Replace pressure switch as necessary.
6. Inspect wiring harness and connectors between pressure switch, ECM and A/C ECU. See «WIRING DIAGRAMS»(ref-98896-S06345939912001060500000). Repair as necessary. If wiring harness and connectors are okay, temporarily substitute a known-good ECM and/or A/C ECU, then retest system.

Scheme 37

Scheme 38