P1603: Engine stall history (Toyota)

Engine stall history

Severity: Inspect soon

On Toyota, P1603 is a record that the engine stalled on its own. The car may restart and run normally, but whatever caused the stall can repeat in traffic, so get it diagnosed soon.

It gets more serious if:

Stop: The engine stalls or loses power while driving, or will not restart. Owners report P1603 with stalls in moving traffic and engine failures. Get off the road safely and have the car towed or checked before driving again.

Source: how we rate severity

P1603 in short

On Toyota vehicles, P1603 means engine stall history: the engine computer recorded that the engine stopped by itself while the ignition was on. It names no faulty part. Fuel delivery, idle or air leaks, a corroded engine computer connector or carbon build-up can all cause it. Get it checked soon; stop if it stalls while driving.

P1603 is a manufacturer code, so its meaning depends on the make. This page covers Toyota, where it is called Engine Stall History.

The engine computer compares crankshaft sensor pulses with the ignition switch. If engine speed drops to zero while the key is still on and nothing told the engine to stop, it stores P1603 to record the stall.

Because it records an event rather than a fault, the code does not say why the engine stalled. It often appears with P1605 (rough idling) and P1604 (startability). Look at any other codes stored with it, such as fuel trim, misfire or sensor codes, and at the freeze-frame data to find the cause.

Pick your make

P1603 is a manufacturer-specific code: its meaning depends on who built the car.

Other makes: meaning not verified. Check with a scan tool that reads manufacturer definitions.

P1603 on Toyota

Most likely causes

Cause 1: Another fault that made the engine stall
Common general cause
Why it ranks here
TAT describes P1603 as a history code that records that a stall happened, not its cause. Owner reports show it stored with sensor, misfire and crankshaft sensor codes after very different failures.
What would change this
Rises when other codes are stored with it; diagnose those first.
Cause 2: Water and corrosion in the engine computer connector (2014-2018 Highlander)
Supported by vehicle data
Why it ranks here
Toyota T-SB-0072-19 lists P1603, P1604 and P1605 with low fuel pressure and drivability problems from water in the A43 engine computer connector, wicked in from poorly sealed aftermarket windshield de-icer harnesses.
What would change this
Applies to the listed Highlanders; rises if an aftermarket windshield with a de-icer is fitted or the connector shows corrosion.
How to test the engine control module (ecm / pcm)
Cause 3: Low fuel pressure or a failing fuel pump
Possible — needs testing
Why it ranks here
Running short of fuel makes an engine stall. Toyota lists low or no fuel pressure with P1603 in its Highlander bulletin, and a Corolla owner's mechanic linked P1603 to a fuel pump recall that did not cover the VIN. The recall does not name the code.
What would change this
Rises if fuel pressure is low or drops during the stall, or a fuel pump recall applies to the VIN.
How to test the fuel pump
Cause 4: Carbon build-up on the pistons (2012-2013 Scion iQ)
Supported by vehicle data
Why it ranks here
Toyota's Scion bulletin S-SB-0008-16 links rough idle, idle dips and P1603, P1604 or P1605 on the iQ to heavy carbon on the piston heads.
What would change this
Applies to the Scion iQ; rises with rough idle and short-trip driving.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

Step 1: Read every stored code and the freeze-frame data, and note engine speed, coolant temperature and battery voltage when it set.
Low riskTool: scan tool
- IfOther codes are stored (fuel trim, misfire, sensor or communication codes)
  It meansDiagnose those first; they most likely explain the stall.
  Points to: Another fault that made the engine stall
- IfOnly P1603, or P1603 with P1604 and P1605
  It meansCheck for a bulletin and test fuel delivery.
  Go to step 2
Step 2: Have a shop check for bulletins and recalls on the VIN, inspect the engine computer connector, and measure fuel pressure at idle and during a stall.
Best left to a shopTool: scan tool, fuel pressure gauge, service information
Warning:Fuel pressure testing opens a pressurised fuel system, which is a fire risk. Leave it to a shop.
- IfCorrosion or water at the engine computer connector
  It meansRepair the connector and seal the source of water.
  Points to: Water and corrosion in the engine computer connector (2014-2018 Highlander)
- IfFuel pressure low or dropping
  It meansDiagnose the fuel pump and supply.
  Points to: Low fuel pressure or a failing fuel pump
- IfA carbon build-up bulletin applies
  It meansFollow the bulletin repair.
  Points to: Carbon build-up on the pistons (2012-2013 Scion iQ)

Symptoms

Engine stalled at a stop or while slowing down
Rough or dipping idle
Check engine light, often with P1604 or P1605
Engine stalls or loses power while driving Gets more serious: stop and have it checked.

How to fix

Step 1: Write down every stored code and the freeze-frame data before clearing anything.
Step 2: Ask a dealer whether a bulletin or recall covers stalling on your VIN.

Parts and cost context

Engine control module (ECM / PCM):P1603 records a stall; it rarely means the engine computer itself has failed. Find the cause before replacing parts.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Toyota

2014–2018 · Highlander
Supported by vehicle data
Check the engine computer connector for water and corrosion if an aftermarket windshield with a de-icer is fitted (T-SB-0072-19).
2018 · RAV4
Possible — needs testing
An owner reports repeated stalls in traffic with P1603, P1604 and P1605 recorded by Toyota and no root cause found. Owner report only.

T-SB-0072-19Status unverified
Toyota T-SB-0072-19: drivability and P1603-P1605 from ECM connector corrosion
2014–2018highlander · issued June 24, 2019 · NHTSA 10162756
Water and corrosion in the A43 engine computer connector, from poorly sealed aftermarket windshield de-icer harnesses, can cause drivability problems, low fuel pressure and codes including P1603, P1604 and P1605.
We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

All Engine computer (ECM/PCM) codes

P1603 questions

My Toyota restarted fine. Do I still need to worry about P1603?

Yes. P1603 only records that the engine stalled; the cause is still there. Check for other codes and have it diagnosed before it stalls somewhere dangerous.

Sources and review

TAT Scandata: P1603 (Toyota) Engine Stall History — Technical Assistance Team (TAT), Australia
NHTSA complaint ODI 11205338: 2018 Toyota RAV4, dealer readout P1603 engine stall, P1605 rough idling — NHTSA Office of Defects Investigation (complaint file) , May 2, 2019
NHTSA complaint ODI 11733489: 2020 Toyota Corolla, P1603 Engine Stall History at a red light — NHTSA Office of Defects Investigation (complaint file) , April 24, 2026
NHTSA complaint ODI 11139909: 2017 Toyota Corolla stalled while driving, P1603 and P1605 — NHTSA Office of Defects Investigation (complaint file) , October 12, 2018
NHTSA complaint ODI 11620473: 2015 Lexus RX engine failure with P0335, P1603, P1604, P1605 — NHTSA Office of Defects Investigation (complaint file) , October 17, 2024
Toyota T-SB-0072-19: Highlander ECM connector corrosion, P1603/P1604/P1605 — Toyota Motor Sales / NHTSA , June 24, 2019
Scion S-SB-0008-16: iQ rough idle, idle dip, P1603/P1604/P1605 — Toyota Motor Sales / NHTSA , October 20, 2016

Last reviewed: October 15, 2026
Written by: Saurabh K.
Editorial review: Pending
Technician review: Technician review pending

This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

Severity: Inspect soon

Pick your make

Most likely causes

Cause 1: Another fault that made the engine stall

Cause 2: Water and corrosion in the engine computer connector (2014-2018 Highlander)

Cause 3: Low fuel pressure or a failing fuel pump

Cause 4: Carbon build-up on the pistons (2012-2013 Scion iQ)

What to test first

Step 1: Read every stored code and the freeze-frame data, and note engine speed, coolant temperature and battery voltage when it set.

Step 2: Have a shop check for bulletins and recalls on the VIN, inspect the engine computer connector, and measure fuel pressure at idle and during a stall.