EN

Severity: High Code type: Manufacturer-specific (Toyota)

Toyota P3191 Code: Engine Does Not Start (Toyota Hybrid)

The hybrid system spun the gas engine with its motor-generator, but the engine never fired up.

Safety first · Consult a professional

  • High-voltage system: hybrid/EV battery circuits (orange cables) can be lethal. Do not open or probe them — leave this to a trained EV technician.

At a glance

Severity: 4/5 – High4/5

Severity: High

Meaning
Engine Does Not Start (Toyota Hybrid)
System
Hybrid / EV · Powertrain
Safe to drive?
No — stop driving
Typical repair cost
$0–$900
DIY difficulty
Moderate

A Toyota hybrid has no conventional starter: when the gas engine is needed, motor-generator MG1 spins it up to roughly 1,000 rpm and the ECM adds fuel and spark. P3191 sets when the engine is cranked this way but doesn't start running within the expected time. Because the car can still creep along on battery power, owners often notice only a 'Check Hybrid System' warning, a quiet engine bay and a battery gauge that keeps falling. By far the most common reason on a Prius is an empty tank, followed by fuel delivery, spark or crank-signal problems; the HV battery is a victim here, not the cause.

How to read P3191

How to read P3191P13213914
  1. P Powertrain
  2. 3 Manufacturer-specific
  3. 1 Fuel & air metering
  4. 91 Specific fault

Symptoms

  • 'Check Hybrid System' message, red triangle and check engine light
  • Gas engine never starts; car moves only on battery power
  • Battery gauge drops steadily until the car shuts down
  • Engine can be heard spinning briefly but doesn't catch
  • Car won't go into Ready after a restart attempt

Possible causes

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

  1. Out of fuel, including cases where the gauge still shows fuel 32%
  2. Fuel pump, fuel pump relay or EFI fuse failure 18%
  3. Crankshaft or camshaft position sensor signal missing 12%
  4. No spark: ignition coil, igniter power or wiring fault 10%
  5. Weak 12-volt battery or poor ground upsetting the start sequence 10%
  6. Very thick oil in cold weather or low compression 10%
  7. Clogged injectors or severely carboned throttle body 8%

Diagnosis step by step

Diagnostic flow: P31911Add fuel first2Read codes and freeze frame3Confirm fuel pump operation4Check spark and engine speed signal5Test the 12-volt battery6Check oil grade and compression

  1. Add fuel first

    Put several gallons of gas in the tank even if the gauge shows fuel remaining. On many Toyota hybrids the start codes then need to be cleared with a scan tool before the system tries to start the engine again.

    Tools: OBD-II scanner

  2. Read codes and freeze frame

    Check which codes accompany P3191 and the engine speed recorded in freeze frame. A crank or cam sensor code, low fuel pressure or P3000 with a low-voltage information code changes where you look next.

    Tools: OBD-II scanner

  3. Confirm fuel pump operation

    With the car in maintenance mode or the engine commanded to run, listen for the pump at the tank and check the EFI fuse and circuit-opening relay. If the scan tool can run the fuel pump active test, the pump should hum clearly.

    Tools: OBD-II scanner, Multimeter

  4. Check spark and engine speed signal

    Watch engine rpm in live data while the system tries to crank; zero rpm while the engine is clearly spinning points to the crankshaft sensor. Check for spark on one coil with an inline spark tester only with the ignition off while connecting it.

    Tools: OBD-II scanner, Flashlight

  5. Test the 12-volt battery

    Measure the auxiliary battery at rest and with Ready requested; it should stay above roughly 11.5 V during the start sequence. A weak 12 V battery can interrupt the start logic.

    Tools: Multimeter

  6. Check oil grade and compression

    Make sure the engine oil is the thin grade the owner's manual specifies, not a heavy oil. If fuel, spark and signals are fine, a compression test shows whether the engine can start at all.

    Tools: Compression tester

Where the parts are

Ignition: coils and spark plugs per cylinder – P31911234567
Ignition: coils and spark plugs per cylinder
  1. 1Ignition coil
  2. 2Spark plug
  3. 3Fuel injector
  4. 4Camshaft sensor
  5. 5Crankshaft sensor
  6. 6Engine computer (ECM)
  7. 7Intake manifold

Repair options & costs

RepairDIY?Estimated cost
Refuel and clear codes Yes $0–$80
Replace 12-volt auxiliary battery Yes $180–$350
Replace fuel pump or pump relay No $150–$900
Replace crankshaft position sensor Yes $150–$350
Replace ignition coil(s) Yes $90–$400

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

Emissions / smog test impact

Will fail

P3191 turns on the check engine light, and a car that can't start its engine can't be tested anyway. Repair it and drive until readiness monitors complete before the smog or emissions test.

Frequently asked questions

My Prius shows fuel on the gauge but set P3191 — could it still be empty?

Yes. Some Prius generations have a fuel gauge that can overstate what is left, especially in cold weather. Adding fuel is always the first and cheapest test.

Why does the car still move if the engine won't start?

The electric motor can drive the car from the HV battery for a while. Once the charge is low, the system shuts down to protect the battery, which is why you shouldn't keep driving.

Will the car restart once I add gas?

Sometimes it does after a few tries, but often the stored codes must be cleared with a scan tool first. If the HV battery was drained very low, a dealer may need to recharge it.

Is P3191 the same as P0A0F?

They describe the same situation, an engine that fails to start. Different Toyota hybrid generations use one or the other, and the diagnosis follows the same logic.

Sources