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Severity: Moderate Code type: Generic (all makes)

P0192 Code: Fuel Rail Pressure Sensor Circuit Low

The rail pressure sensor signal voltage has fallen below the lowest value a working sensor can produce.

At a glance

Severity: 3/5 – Moderate3/5

Severity: Moderate

Meaning
Fuel Rail Pressure Sensor Circuit Low
System
Fuel & Air Metering · Powertrain
Safe to drive?
With caution
Typical repair cost
$60–$1,500
DIY difficulty
Moderate

A healthy rail pressure sensor never outputs much less than about 0.5 volt, even with zero pressure in the rail, so the PCM treats anything below roughly 0.2 to 0.3 volt as a circuit fault and sets P0192. That means the voltage is being pulled toward ground: the signal wire is shorted to ground, the 5-volt reference feeding the sensor has collapsed, or the sensor itself has failed internally. A very common twist is a shared reference: several sensors often hang on the same 5-volt supply, and one shorted sensor elsewhere on the engine drags them all down, which is why P0192 often arrives together with other 'circuit low' codes. Because the PCM now reads zero pressure, diesels typically refuse to start and gasoline engines fall back to a fixed limp strategy.

Can I keep driving? If it still runs, drive gently and directly to a shop. A diesel that stalls with this code usually won't restart, so don't shut it off far from help.

How to read P0192

How to read P0192P10213924
  1. P Powertrain
  2. 0 Generic (SAE)
  3. 1 Fuel & air metering
  4. 92 Specific fault

Symptoms

  • Cranks normally but won't start (diesel), or starts only after long cranking
  • Engine dies and the scan tool shows 0 psi rail pressure
  • Several sensor 'circuit low' or reference voltage codes stored together
  • Gasoline engine runs in limp mode with reduced power
  • Fault set right after work near the sensor or a harness repair

Possible causes

Ranked by how often each cause is behind this code (editorial estimate).

  1. 5-volt reference pulled down by another shorted sensor on the same circuit 28%
  2. Signal wire shorted to ground through chafed insulation 24%
  3. Rail pressure sensor internally shorted 22%
  4. Open 5-volt reference wire to the sensor 12%
  5. Water or corrosion bridging pins inside the connector 9%
  6. PCM reference supply or input failure 5%

Diagnosis step by step

Diagnostic flow: P01921Look at every stored code2Measure the reference at theconnector3Jumper test the signal circuit4Check the signal wire for a short toground5Inspect the connector for moisture

  1. Look at every stored code

    Several low codes from sensors such as MAP, throttle, pedal or boost together with P0192 point to a shared 5-volt reference problem. P0192 alone points to the rail sensor or its own wiring.

    Tools: OBD-II scanner

  2. Measure the reference at the connector

    Unplug the rail sensor and turn the key on. The reference pin should read 4.8 to 5.2 volts. If it's low or zero, unplug the other sensors on that reference one at a time; when the voltage suddenly returns, the last sensor you unplugged is the shorted one.

    Tools: Multimeter

  3. Jumper test the signal circuit

    With the sensor unplugged, connect a fused jumper from the reference pin to the signal pin in the harness plug. The scan tool should jump to maximum pressure (and P0193 may set). If it does, the wiring and PCM are good and the sensor is at fault; if it stays at zero, the signal wire or PCM is the problem.

    Tools: Multimeter, OBD-II scanner

  4. Check the signal wire for a short to ground

    Battery disconnected, sensor and PCM unplugged: measure the signal wire to ground. Anything below several thousand ohms is a short. Split the harness into sections at connectors to narrow down where the insulation is damaged.

    Tools: Multimeter

  5. Inspect the connector for moisture

    Look inside both halves for water, fuel or green deposits bridging the pins. Dry and clean it, check each terminal's grip, and seal it properly before replacing any parts.

    Tools: Flashlight, Screwdriver

Where the parts are

EVAP system: gas cap, canister, purge and vent valves – P0192123456
EVAP system: gas cap, canister, purge and vent valves
  1. 1Gas cap
  2. 2Charcoal canister
  3. 3Purge valve
  4. 4Vent valve
  5. 5Fuel pump
  6. 6Intake manifold

Repair options & costs

RepairDIY?Estimated cost
Replace another shorted sensor on the shared reference Yes $60–$300
Repair chafed signal or reference wire Yes $100–$350
Rail pressure sensor replacement No $150–$450
Fuel rail with integrated sensor (diesel) No $600–$1,400
PCM repair or replacement and programming No $600–$1,500

Rough US estimates for parts and labor; shop rates vary by region. Not a quote.

Notes by brand

Field data

Mazda 13 CX-5, CX-9, CX-3

Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.

Emissions / smog test impact

Will fail

A stored P0192 with the check engine light on fails any OBD-II based emissions inspection, and a car that won't start can't be tested anyway. Repair it and let the monitors complete first.

Frequently asked questions

Can very low fuel pressure cause P0192?

No. Even with the rail completely empty, a working sensor still outputs about half a volt. P0192 is about the voltage going below what the sensor can physically produce, so the cause is electrical. A real low-pressure problem sets P0087 instead.

Why do I have five different codes at once?

Many engines feed several sensors from one 5-volt reference. If one of them shorts internally, the reference collapses and every sensor on it reads low. Fix the one shorted sensor and the whole group usually clears.

Will a new sensor fix it?

Only if the jumper test proves the wiring and PCM are good. Replacing the sensor first is a common and expensive mistake, especially on diesels where it may mean buying the entire rail.

Sources