P1423 — Split Air #1 Circuit Malfunction

For Ford vehicles

exhaust gas ignition functional test

powertrain (engine/transmission)

Is it safe to drive?

Short-term driving is OK In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How to diagnose with an OBD scanner

  1. Read the code and freeze frame Connect an OBD2 scanner, confirm P1423 is stored, and save the freeze frame data — it shows engine conditions when the fault was detected.
  2. Check for companion codes and TSBs Related codes often reveal the real root cause. Also check manufacturer technical service bulletins (TSB) for your make and model — many P0xxx issues have factory fixes or software updates. Search by VIN on the manufacturer site or nhtsa.gov.
  3. Inspect wiring and connectors Visually inspect the wiring harness and connectors related to the split air #1 for damage, corrosion, chafing or poor contact.
  4. Subsystem check Run the module's actuator test for the split air #1 if your scanner supports it — a component that does not respond to a direct command is confirmed faulty.
  5. Subsystem check Measure reference voltage, ground and signal continuity at the component connector.
  6. Subsystem check Wiggle-test the harness while watching the signal in live data — dropouts reveal broken wires.
  7. Verify the repair Clear the code, complete a full drive cycle including the conditions from the freeze frame, and confirm P1423 does not return.

Approximate repair cost

Repair cost depends on which component actually failed. Typical scenarios for P1423 (parts and labor, USD, independent shop rates): Replace the faulty sensor or actuator: $150–$500; Repair wiring or connectors: $80–$250; Control module repair: $300–$1,000. Overall, fixing P1423 usually costs between $80 and $1,000. An accurate diagnosis before buying parts saves money — the most expensive scenario is rarely the first one to check.

Common questions

Is it safe to drive with P1423?

In most cases the car remains drivable, possibly with reduced performance or a disabled auxiliary system. If symptoms include stalling, no-start or brake/steering warnings, treat it as urgent.

How do I diagnose P1423 myself?

Start with a scan: confirm P1423, save the freeze frame and note any companion codes. Then inspect the wiring and connectors related to the split air #1, and verify the suspect component against live data before buying parts.

Will P1423 clear itself?

Sometimes P1423 clears after a few drive cycles if the fault was intermittent — for example a loose connector or a tank of bad fuel. The underlying cause usually remains, so the code tends to return. Clear it once; if it comes back, diagnose rather than erase it repeatedly.

What are the symptoms of P1423?

Drivers most often notice: possible limp mode depending on the affected component, increased fuel consumption in some cases, the affected system operates intermittently or not at all, Check Engine Light on.

What is the most common cause of P1423?

The most common causes are: open or shorted wiring in the circuit, faulty sensor or actuator of the affected circuit, corroded, loose or damaged connector.

When your check engine light illuminates and a scan tool reveals code P1423, it points to a specific fault with a component known as the split air #1 circuit. This generic powertrain code is stored by the engine control module (ECM) or powertrain control module (PCM) after its internal self-diagnostics detect that this particular circuit has failed an electrical or functional test. P1423 essentially means the computer has verified a problem exists and cannot correct it through its normal adaptive strategies.

The split air #1 system plays a role in either emissions control or engine performance management, depending on your vehicle's design. The ECM continuously monitors this circuit while the engine runs, comparing real-time sensor data against programmed acceptable values. When readings drift outside the defined range for a set number of drive cycles, the module stores P1423 and turns on the warning light. The freeze frame data captured alongside this code is invaluable—it records engine RPM, load, temperature, and vehicle speed at the exact moment the fault was detected, giving you precise conditions to reproduce during testing.

Symptoms of P1423

  • The Check Engine light is illuminated and remains on
  • The split air #1 system may function intermittently or not at all
  • Reduced engine performance or limp-mode operation in some vehicles
  • Noticeable increase in fuel consumption compared to normal
  • Possible auxiliary system failures depending on which component is affected

Common Causes of P1423

  • Internal failure of the split air #1 sensor or actuator
  • Wiring or connector damage preventing proper circuit operation
  • Corroded, loose, or physically damaged electrical connector at the component
  • Blown fuse or open fusible link feeding power to the circuit
  • Poor or interrupted ground connection at the component or module
  • Control module driver circuit or software calibration fault
  • Short-to-ground or short-to-power fault in the signal circuit

How to Diagnose P1423

  1. Connect an OBD2 scanner and verify P1423 is stored in the PCM. Record all freeze frame data—this shows exactly what the engine was doing when the fault occurred and guides your test conditions.
  2. Note any other stored trouble codes. Related codes often point to the underlying cause, whether it's a power supply issue, ground problem, or secondary component failure.
  3. Search manufacturer technical service bulletins (TSB) for your make, model, and model year. Many P0xxx codes have known factory fixes, software updates, or documented issues with specific components.
  4. Perform a thorough visual inspection of all wiring and connectors related to the split air #1 circuit. Look for damaged insulation, broken wires, corrosion buildup, and any signs of previous repairs that may have failed.
  5. Check for power, ground, and signal voltage at the component connector using a multimeter. Compare your readings to manufacturer specifications. Run an actuator test if your scanner supports it—a component that ignores direct commands is confirmed defective.
  6. Perform a wiggle test on the harness while monitoring live data. Any signal dropouts or interruptions indicate broken wires inside the insulation that only show under movement.

Repair Options and Costs

If diagnosis confirms the split air #1 component itself has failed internally, replacement typically runs $150–$500 for parts and labor. Repairing damaged wiring, connectors, or terminals generally costs $80–$250 depending on the extent of the damage and whether connector replacement is necessary. In rare cases where the control module's driver circuit for this system has failed, ECM or PCM repair can range from $300–$1,000.

Total Repair Cost for P1423

The actual cost to fix P1423 varies based on which part fails. Parts and labor at independent shop rates in USD typically break down as follows: sensor or actuator replacement $150–$500, wiring or connector repair $80–$250, and control module repair $300–$1,000. Most P1423 repairs fall between $80 and $1,000 total. Always pursue accurate diagnosis before purchasing parts—the most expensive scenario is rarely the first place to start, and many electrical issues resolve with simple connector cleaning or harness repair.

Can You Drive with P1423?

Most vehicles remain driveable when P1423 is stored, though you may experience reduced performance, slightly higher fuel consumption, or a disabled auxiliary system. The car will not typically stall or fail to start due to this code alone. However, if you notice stalling, hard starting, or warnings affecting brakes or steering, treat the situation as urgent. Otherwise, schedule diagnosis and repair within a reasonable timeframe to prevent potential emissions test failures and avoid secondary damage from an unresolved electrical fault.

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