Toyota P1604 records an unsuccessful start event; it does not name the starter. Toyota's 2010 1GR-FE description includes extended cranking or engine speed falling very low shortly after start and says to check whether the vehicle ran out of fuel. Classify the event first: no crank, slow crank, normal crank/no fire, or start then stall. Save battery voltage, cranking rpm, immobilizer state, fuel pressure, MAF/throttle and companion codes during the failure. T-SB-0009-23 provides a fuel-pressure branch for specified 2014–2019 4Runners. The flex-fuel P1604 bulletin commonly found online covers 3UR-FBE Tundra/Sequoia, not the 4Runner.
Match the symptom
Select the closest observation. The result changes the first test; it does not name a part to replace.
Test battery, cables, start authorization and starter circuit before engine fueling.
What can set P1604—and how to separate it
The order below is evidence-driven, not a universal probability ranking. Vehicle year, repair history, companion codes and the operating condition in freeze frame change where diagnosis should begin.
| Possible cause | Evidence that supports it | First useful test |
|---|---|---|
| Weak battery, cable resistance or starter problem | Low cranking voltage/speed or excessive drop | Battery load/conductance and voltage-drop test |
| Fuel-pressure loss or empty/contaminated fuel | Low pressure during failure, hard start or P0087 | Measure pressure during the start event |
| Immobilizer or start-authorization fault | Security indication or companion body/immobilizer code | Scan all modules and verify authorization |
| Crank signal, ignition or injector failure | No rpm/sync, spark or injection command | Simultaneous cranking signal tests |
| Air, throttle, purge or mechanical compression problem | Implausible air data, post-refuel stall or low relative compression | Intake/purge and relative-compression checks |
Classify before connecting a parts list
A silent no-crank focuses attention on power, control and authorization. Normal-speed cranking with no combustion shifts the test toward sync, fuel, ignition and compression.
A start/stall event adds throttle, purge and early-run data. Record elapsed run time rather than grouping every failure under 'hard start.'
Measure the pump during failure
Pressure can look normal after a second attempt primes the system. Begin recording before the start request and retain the failed trace.
The 2014–2019 Toyota bulletin creates a legitimate pump branch for exact applications; it does not replace measurement or eligibility checks.
Prepare for remote reliability, not just one shop start
Heat soak, overnight cold, low tank level and vehicle angle can expose intermittent problems. Repeat the conditions safely after repair.
Before trail use, confirm battery reserve and reliable restarts without pending codes. A vehicle that starts once in a bay is not necessarily dependable miles from assistance.
Save these scan-data clues
Freeze frame is a snapshot of conditions when the PCM matured the fault. It can distinguish an idle-only problem from a load, cold-start or monitor-completion problem. Clearing first throws that context away.
- Battery voltage and cranking rpm
- Engine run time before stall
- Fuel pressure during the failed event
- MAF, throttle and coolant temperature
- Immobilizer, crank/cam and companion codes
- Fuel level, recent service and environmental conditions
A practical diagnostic workflow
- 01Name the failed start type
No-crank and crank/no-start are different diagnostic problems despite one customer description.
- 02Save all-module evidence
P1604 is often secondary; companion immobilizer, fuel or signal codes may be more specific.
- 03Test electrical cranking integrity
Measure voltage and drop under load, not with a resting battery reading alone.
- 04Capture fuel, spark and sync together
Avoid repeated starts that let a marginal pump recover or drain the battery.
- 05Prove air and compression
Check throttle/MAF plausibility, purge sealing and relative compression as evidence requires.
- 06Verify hot and cold restarts
A single successful start does not prove an intermittent heat-soak or cold fault repaired.
Do not install a starter or ECM because P1604 appeared. It can be stored after empty fuel, weak battery, low pressure, immobilizer denial, missing crank signal, purge flooding or mechanical problems. Do not apply the 3UR-FBE flex-fuel Tundra/Sequoia bulletin to a 4Runner.
Why the model year changes the test
U.S.-market 4Runner diagnostics span the 1996–2002 3RZ-FE four-cylinder and 5VZ-FE V6, the 2003–2009 1GR-FE V6 and optional 2UZ-FE V8, the long-running 2010–2024 1GR-FE V6, and the 2025+ turbocharged 2.4L powertrains including i-FORCE MAX. Bank layout, fuel and EVAP hardware, VVT strategy and monitor logic differ. Off-road dust, water crossings, skid-plate work, auxiliary wiring and modified intakes add failure paths that sedan-oriented guides often miss. Confirm VIN, model year, engine, emissions label and modifications before testing.
- The 2010 1GR-FE Toyota description notes both extended cranking and a start followed quickly by very low rpm/stall.
- 2014–2019 4Runner is listed in T-SB-0009-23's fuel-pump pressure-loss applicability.
- The 3UR-FBE flex-fuel bulletin T-SB-0166-19 lists Tundra and Sequoia, not 4Runner.
- Remote/off-road use makes a repeatable hot and cold restart check especially important before return to service.
P1604 FAQ
Does P1604 mean a bad starter?+
No. It records a failed start event; electrical, fuel, ignition, air, authorization and mechanical causes remain possible.
Can running out of fuel set it?+
Yes. Toyota's 1GR-FE description specifically says to check that history.
Can a weak battery cause it?+
Yes. Low voltage and cranking speed can prevent ignition and distort other signals.
Is the fuel pump bulletin automatic coverage?+
No. Verify model/VIN/VDS eligibility and demonstrate pressure loss.
Does the flex-fuel bulletin apply?+
No. The cited bulletin names 3UR-FBE Tundra and Sequoia applications.
Should I keep cranking?+
No. Repeated attempts drain the battery, heat the starter and can hide the original pattern.
Can P1604 be historical?+
Yes. Interpret it with occurrence data, companion codes and current restart reliability.
What confirms repair?+
Normal voltage, pressure and signals plus repeated hot/cold starts without a pending event code.
Ford diagnostic references
These documents explain Ford monitor operation. Exact pinpoint tests, connector views and specifications must be selected for the truck's VIN and model year in current service information.
01Toyota 2010 4Runner 1GR-FE P1604 descriptionDefines the startability event and lists battery, fuel, ignition, immobilizer, sensors, air and mechanical causes↗02Toyota T-SB-0009-23 — fuel-pump pressure lossIncludes 2014–2019 4Runner among specifically listed applications; VIN/VDS and program eligibility must be confirmed↗03Toyota 4Runner manuals and warranty guidesOfficial Toyota model-year lookup; confirm VIN, engine, drivetrain and emissions certification↗04Toyota Technical Information SystemToyota's current North American repair manuals, wiring diagrams, bulletins and calibration information↗