B1423 – Pressure sensor circuit open/refrigerant pressure abnormal (Lexus)

B1423 means your Lexus has detected a problem with the A/C refrigerant pressure sensor input, so the air conditioning may stop cooling or cycle on and off. Most drivers notice weak cooling first, especially at idle or in traffic. According to Lexus factory diagnostic data, this code indicates a pressure sensor circuit open or refrigerant pressure abnormal. This is a manufacturer-specific Lexus body code, so the exact monitor logic can vary by platform and calibration. On a 2021 RX400h, treat it as a strong clue toward the pressure sensor circuit and the pressure value the A/C control uses for compressor control and system protection.

B1423 Quick Answer

B1423 on Lexus points to an open circuit to the refrigerant pressure sensor or a pressure reading the system considers abnormal. Confirm the sensor signal, power, and ground at the connector before replacing any parts.

What Does B1423 Mean?

Official definition: “Pressure sensor circuit open/refrigerant pressure abnormal.” In plain terms, the A/C control system cannot trust the refrigerant pressure information. When that happens, Lexus logic usually limits or disables compressor operation to protect the system. That leads to poor cooling, intermittent cooling, or no A/C.

What the module actually checks: the control module monitors the pressure sensor circuit for electrical integrity and a believable pressure value. It looks for an “open” type fault (missing or invalid signal) and for pressure behavior that does not match expected operating conditions. Why it matters: this DTC does not prove the sensor failed. It only points to the sensor circuit and pressure plausibility as the suspected trouble area, so circuit testing and basic A/C system checks must come first.

Theory of Operation

Under normal conditions, the refrigerant pressure sensor reports system pressure to the Lexus A/C control logic. The module uses that input to command compressor operation and manage condenser fan strategy. It also uses pressure feedback as a safety limit to prevent damage.

An open circuit, poor connection, or wiring fault can remove the pressure signal from the module. A true refrigerant issue can also create “abnormal pressure” behavior the module flags as implausible. Once the module sees the fault, it may inhibit compressor engagement or force a protective mode until the signal returns and the code clears.

Symptoms

You will usually notice A/C performance problems first with this Lexus-specific B1423 code.

• No cooling A/C blows warm air because the system disables compressor operation
• Intermittent cooling A/C cycles between cold and warm as the signal drops out
• A/C warning HVAC indicator or message related to A/C operation, depending on cluster configuration
• Compressor inhibited Compressor command stays off even when requested
• Cooling fan behavior Condenser/radiator fan operation may run unexpectedly or not match heat load
• Stored body DTC B1423 sets in the HVAC/A/C related module and may return quickly after clearing
• Freeze-frame clues Scan data may show an out-of-range or missing pressure value at the time of the fault

Common Causes

• Open in the pressure sensor signal circuit: A broken signal wire prevents the Lexus A/C control module from seeing a valid pressure signal.
• Open in the sensor 5V reference feed: Loss of the regulated reference supply makes the sensor output drop out or read implausibly.
• Open or high resistance in the sensor ground circuit: A weak ground skews the sensor output and can look like an open circuit to the module.
• Connector terminal spread, push-out, or corrosion at the pressure sensor: Poor terminal contact creates an intermittent open, often worse with vibration and heat.
• Harness damage near the condenser, compressor area, or radiator support: Chafing or pinch points open the circuit as the harness moves with engine torque and road vibration.
• Refrigerant pressure actually abnormal due to low charge or restriction: Real pressure faults can trigger an abnormal pressure rationality failure even when wiring looks intact.
• Refrigerant overcharge or non-condensable contamination: Excess pressure or unstable pressure causes implausible sensor readings during commanded A/C operation.
• Pressure sensor internal failure: An internal open in the sensor electronics can mimic an open circuit even with good wiring.
• Control module input fault or shared reference/ground issue: A problem inside the Lexus A/C amplifier or a shared sensor feed can pull the circuit out of range.

Diagnosis Steps

You need a scan tool that can read Lexus body/A/C data, command A/C functions, and view freeze frame. Use a quality DVOM, back-probe pins, and wiring repair tools. A manifold gauge set helps confirm abnormal refrigerant pressure, but you must follow safe refrigerant handling practices. Use service information for connector views and circuit routing.

1. Confirm DTC B1423 and record all related codes. Save freeze frame data and note battery voltage, ignition state, A/C request status, compressor command, and reported refrigerant pressure. Freeze frame shows conditions when the fault set. Use a scan tool snapshot later to catch intermittent dropouts during a wiggle test or road test.
2. Check basic power distribution first. Inspect A/C-related fuses, fusible links, and relay feeds that support the A/C amplifier, compressor control, and sensor supply circuits. Do a quick visual inspection of the pressure sensor circuit path at the front of the vehicle before meter work. Look for rubbed-through loom, impact damage, and recent repairs near the condenser or radiator support.
3. Verify module power and grounds under load. Turn the system on so the A/C control module energizes its circuits. Perform voltage-drop tests on the module grounds while the module operates. Keep ground drop under 0.1V with the circuit active. A clean continuity check does not catch a high-resistance connection.
4. Inspect the pressure sensor connector and terminals closely. Check for terminal spread, backing-out, water intrusion, and green corrosion. Tug lightly on each wire at the connector. If the vehicle recently had front-end service, look for a pinched connector or misrouted harness.
5. Use scan data to judge whether the issue looks like an open circuit or an abnormal pressure condition. With ignition ON and A/C commanded, watch the pressure PID. A hard open often shows a fixed extreme value or a reading that drops out. An actual pressure issue usually shows plausible changes that do not match A/C command and ambient conditions.
6. Check the 5V reference at the pressure sensor connector with ignition ON. If the reference feed is missing, locate the shared reference splice and any other sensors on that feed. Unplug related sensors one at a time and recheck the reference supply. A shorted sensor on a shared feed can pull the reference down and mimic an open at the pressure sensor.
7. Check sensor ground integrity with a voltage-drop test. Keep the sensor connected and the circuit operating. Measure voltage drop from the sensor ground pin to battery negative while the system runs. Excess drop points to corrosion, a loose ground point, or a damaged ground wire.
8. Check the signal circuit for an open and for signal integrity. Back-probe the signal wire at the sensor and at the module side if access allows. Compare readings while you gently flex the harness. If the signal disappears during movement, isolate the exact section by working along the harness in smaller zones.
9. If wiring checks pass, confirm whether refrigerant pressure is actually abnormal. Compare scan-tool pressure to manifold gauge readings if available. Then verify condenser airflow, cooling fan operation, and obvious restrictions. A cooling fan problem can push high-side pressure out of range and set an abnormal pressure fault without a sensor circuit defect.
10. Clear codes and run a verification test. Command A/C operation and monitor live data for stable pressure readings and consistent compressor request/command behavior. Recheck for pending versus confirmed status after a drive cycle. Many body/A/C codes can return immediately on key-on when a hard open exists, so an instant reset points back to wiring, terminals, or sensor supply.

Professional tip: Treat B1423 as a suspected trouble area, not a failed part. On Lexus platforms, a pressure sensor circuit can share reference or ground with other inputs. Always prove the 5V reference and ground with voltage-drop testing before you condemn the sensor. Use a scan tool snapshot during a harness wiggle test to catch a one-frame pressure drop that freeze frame cannot show.

Possible Fixes

• Repair open/high-resistance wiring in the pressure sensor circuit: Restore continuity and proper terminal tension, then retest with live data and a wiggle test.
• Clean, repair, or replace damaged connector terminals: Correct push-outs, corrosion, and loose pins at the sensor and module connectors.
• Restore 5V reference or ground path integrity: Repair shared splices, ground points, or harness sections proven bad by voltage-drop results.
• Correct the refrigerant pressure abnormal condition: Address verified low charge, overcharge, restriction, or airflow/fan issues using proper A/C service procedures.
• Replace the refrigerant pressure sensor only after circuit proof: Install a sensor only when tests confirm correct power, ground, and signal wiring but the sensor output remains invalid.
• Address a module-side input fault only after isolation: Consider A/C amplifier or control module input issues only after you eliminate wiring, terminal, and pressure causes.

Can I Still Drive With B1423?

You can usually drive a 2021 Lexus RX400h with B1423, but expect the HVAC system to limit A/C operation. Lexus uses the refrigerant pressure input to protect the electric compressor and related components. When the module sees an open circuit or an abnormal pressure signal, it often disables compressor command or cycles it off. That protects hardware, but it reduces cabin cooling and defogging performance. Avoid long drives in hot weather if you need reliable windshield clearing. Also avoid repeatedly commanding MAX A/C. That habit can stress connectors and wiring when the fault is intermittent.

How Serious Is This Code?

B1423 usually lands in the “inconvenience to moderate” category. You will not lose basic vehicle control, and it does not create an immediate brake or steering risk. The bigger impact comes from climate control function. Reduced A/C can hurt visibility during humid or rainy conditions because the system may not dehumidify well. On a Lexus hybrid platform, the A/C compressor protection logic matters. An incorrect pressure signal can cause the module to inhibit compressor operation to prevent damage. Treat it as a priority repair if you rely on defogging, if the A/C cycles rapidly, or if other HVAC-related codes appear.

Common Misdiagnoses

Technicians often replace the pressure sensor first because the description mentions “pressure sensor.” That wastes money when the real problem is an open in the sensor signal, a spread terminal at the connector, or corrosion in the harness near the condenser. Another common miss involves refrigerant charge. Low charge can set pressure plausibility faults, but it cannot create a true circuit open. Verify the electrical side before connecting gauges. People also confuse a blown HVAC fuse with a sensor fault. Confirm sensor power, ground integrity, and signal continuity under load before condemning any component.

Most Likely Fix

The most frequent confirmed repair path for B1423 on Lexus platforms involves restoring circuit integrity at the refrigerant pressure sensor harness. Start with connector pin fit, water intrusion evidence, and harness damage at the front of the vehicle. If tests show the sensor loses its reference feed, ground, or signal path to the HVAC/AC control logic, repair the wiring and terminals, then verify stable pressure PID behavior. Replace the pressure sensor only after you prove correct power and ground at the connector and you confirm the signal stays invalid with a known-good circuit.

Repair Costs

Repair cost depends on whether the confirmed root cause is a sensor, wiring, connector issue, or control module problem. Verify the fault electrically before replacing parts.

Last updated: April 3, 2026