Maintenance

Camry generations five and six: A brief tour of the Toyota Camry fuel and EVAP systems

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Camry generations five and six: A brief tour of the Toyota Camry fuel and EVAP systems

 

Jacques Gordon has worked in the automotive industry for 40 years as a service technician, lab technician, trainer and technical writer. His began his writing career writing service manuals at Chilton Book Co. He currently holds ASE Master Technician and L1 certifications and has participated in ASE test writing workshops.

Since the day it was introduced to the U.S. market, the Toyota Camry has been one of the most reliable cars on the road. With normal maintenance or even a fair amount of neglect, it seems these cars almost never break down. When problems do arise, the diagnosis is rarely a challenge.

But diagnosis is always faster and more accurate when you know more about the vehicle. If you don’t normally work on Toyotas, or if you simply haven’t had the opportunity to look into a Toyota fuel system lately, here’s a quick overview of the two most common models.

The 2002-2006 model is the Camry’s fifth generation and the first year for the 2.4-liter 2AZ-FE engine with an electronic mass airflow sensor, electronic throttle and a returnless fuel injection system. That system architecture became the model for Toyota port fuel injected engines right up through current generation, including the other engines used in that car, the 3.0-liter 1MZ-FE and the 3.3-liter 3MZ-FE.

Returnless fuel systems were developed to reduce evaporative emissions. The main difference is the fuel pressure regulator is inside the fuel tank instead of under the hood. The fuel rail may have something that looks like a pressure regulator, but it’s actually a pulse damper to reduce pressure pulsation and fuel pump noise. The mechanical pressure regulator is part of the fuel pump module that includes the pump, a reservoir, the gauge sending unit and a fuel filter.

The fuel pump module is usually sold as a complete assembly, but according to the service manual each of those components can be replaced separately once the module is removed. That includes the only fuel filter in the whole system, the strainer or “sock” on the inlet side of the pump. Turbine pumps are not particularly strong on the suction side, so if there’s a no-start or driveability issue that’s caused by lack of fuel, the problem just might be nothing more than a clogged fuel filter.

Specs for this fuel system are the same for all three engines: fuel pressure with the engine running or not running is 44 to 50 psi, hold pressure is 21 psi and fuel injector resistance is 11.6 to 12.4 ohms at 68 degrees Fahrenheit (20 degrees Celsius).

There is no fuel pump flow rate specification, and there’s no pressure tap on the fuel rail either. One way to check fuel volume is to monitor fuel pressure during full-throttle acceleration. If fuel pressure falls below specification during a full-throttle acceleration, that means the fuel pump can’t keep up with the demand.

The fuel injection system’s electrical circuit design is the same on all three engines, but it is uniquely Toyota. Power for the fuel pump is supplied by what they call the circuit-opening relay (C/OPN), which any other manufacturer would simply call the fuel pump relay. Like other cars, power for the relay coil comes from the ignition switch (through a 10-amp fuse), and the ground circuit is provided by the PCM when the ignition switch is in the START position or when engine speed is above cranking speed.

What’s different here is that power for the C/OPN relay contacts is supplied by the main electronic fuel injection (EFI) relay, and power for this relay coil is provided by the PCM. Depending on the model, the EFI relay provides power to the fuel pump (through the C/OPN relay) the EVAP purge valve (VSV) and/or an oxygen sensor heater. This means you can’t really determine fuel pump voltage or current draw at the C/OPN relay socket, you’ll need to check it at the fuel pump connector itself. Fortunately that’s easily reached through the access panel under the rear seat.

By the way, Toyota OEM wiring diagrams are some of the most informative and user-friendly, and they often include notes about voltage, resistance and signal specs at the terminal connections.

Despite the Camry’s reputation for reliability, this was the first generation designed to meet LEV II evaporative emissions regulations. That means EVAP codes are common on these models because the EVAP system is relatively complicated: It includes the charcoal canister with a pressure sensor, two solenoid valves and some sophisticated software. The purge valve is under the hood, but the vent valve and pressure sensor are part of the canister assembly, and that’s mounted underneath right next to the fuel tank. This makes it easier to flood the canister if the tank is overfilled.

A complete and detailed service bay test is available in Toyota Service Bulletin EG048-04.

We’ll describe how the onboard EVAP monitors work here.

The PCM runs two different EVAP purge monitors to test the vacuum switching valve (VSV). That’s what Toyota calls the purge valve because it’s switched on and off in a duty cycle to control how much vacuum is applied to the canister. When the engine is running and all the normal drive-cycle criteria are met, the PCM turns on the canister closed valve (CCV), commonly called the vent valve. The CCV is normally open, so turning it on closes it. With the CCV closed, the PCM cycles the VSV and monitors the pressure sensor in the canister. If canister pressure doesn’t decrease during this test, the CCV is turned off (opened) and the PCM looks for a pressure increase of at least two inches of water (3.75 mmHg). If pressure still doesn’t change, the PCM decides the VSV is not opening and a pending code will be recorded in memory. If this happens on two consecutive trips, the PCM will illuminate the MIL and set code P0441 (purge flow incorrect).

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In the other test, the PCM reads atmospheric pressure (there’s a “baro” sensor inside the PCM) with the engine running and the VSV and CCV both closed. If pressure inside the canister goes below atmospheric pressure, the PCM decides the VSV is stuck open. A pending code will be recorded in memory, and if this happens on two consecutive trips, the PCM will illuminate the MIL and set code P0441 (purge flow incorrect).

The CCV is tested the same way. With the CCV commanded closed (turned on) and the VSV commanded open, the PCM expects to see high vacuum in the canister. If not, the CCV is not closing. When the canister is at atmospheric pressure and both valves are commanded open, the PCM expects to see no pressure change in the canister. If the canister develops negative pressure for more than four seconds, the CCV is not opening. A pending code will be recorded, and if this happens on two consecutive trips, the PCM will illuminate the MIL and set code P0446 (vent valve circuit malfunction).

The vent passage goes through a filter and terminates in the fuel filler tube. Toyota says the filter can become clogged, but EVAP codes have also been caused by spider nests in that passage.

To leak-test the fuel tank and EVAP system, the PCM simply closes the CCV and opens the VSV to draw a vacuum on the system with the engine running. After closing the VSV, it measures the time required for the vacuum to decay. If there is a leak, the rate of pressure rise determines which fault code will be set: P0442 (large leak) or P0456 (small leak) or P0455 (gross leak). This is also a two-trip test that sets a pending code on the first failure and a hard code on the second consecutive failure.

Sixth generation

The next (sixth) generation Camry is the 2007-2011 model. The 2AZ-FE engine carries over with the same fuel injection system, but now the C/OPN relay coil shares a power circuit with the injectors. There’s also a new 3.5-liter 2GR-FE six-cylinder engine.

This is the first year that the EVAP system has a dedicated Leak Detection Pump (LDP). All of the other components and most of the operating strategy remain the same, except for the leak test.

The EVAP system leak test runs only if there are no codes or pending codes for the valves. After the engine has been turned off for five hours (to let fuel tank pressure stabilize), the PCM wakes up, reads ambient pressure, turns on the CCV to close the vent, then operates the LDP. Remember, the purge valve is normally closed, but in this system, closing the CCV doesn’t actually seal the system; it connects the LDP to a 0.020-inch reference orifice. Air flows out of the canister through the reference orifice while the PCM monitors the decrease in canister pressure. If it decides there is a leak, it sets a pending code. If the test is failed again after the next drive/rest cycle, the PCM will illuminate the MIL and store the appropriate leak code(s). There are also sensor failure codes (P0450, P0451, P0452, P0453) plus a number of Toyota-specific codes for the valves and pump.

The EVAP monitors can be commanded to run with a scan tool, which is good because it’s possible for local conditions to prevent it from running automatically. If battery voltage falls below 10.5, the test will be aborted. If coolant temperature is not between 40 and 95 degrees F (4 – 35 degrees C) within five hours after shut-down, the PCM will wait two more hours and try again. A third attempt will be made after another 2.5 hours. If pressure altitude is greater than 8,000 feet, the monitor will not run.

Incidentally, the LDP makes noise when it runs, which sometimes causes customers to ask why their car is making strange noises while parked in the garage overnight.

Smart key

The sixth generation Camry is the first available with an optional Smart Key system that has an Engine Start button in place of an ignition key.

The Smart Key system adds a major layer of complexity because some engine operations are controlled by what Toyota calls the main body ECU (aka body control module or BCM). The fuel pump is still operated by the C/OPN relay, and power for that relay’s contacts still comes from the main EFI relay. However, power for the C/OPN relay coil comes from a third relay labeled IG2 (ignition 2) that also provides power to the injectors. Power for the IG2 coil comes from the BCM when the Smart Key is detected.

On the Smart Key system, the BCM and the PCM control the starter together. When the Engine Start button is pushed, various on-board control units verify that the correct key has been detected in the vehicle, and then accessory power is turned on by the BCM. When the Start button is pressed with the gear selector in Park or Neutral and the brake pedal depressed, the BCM activates both ignition relays, unlocks the steering and sends a “start” request to the PCM. The PCM will then request a cut in accessory power (from the BCM) while it activates the starter relay. Once engine speed reaches 1,200 rpm, it will release the starter relay and terminate the accessory-cut request.

If the brake light switch or circuit fails, the engine can still be started by pressing the engine Start button once to turn on accessory power, then pressing it again and holding it for 15 seconds. If there is no fuel in the tank (or if the fuel gauge sending unit fails), the start sequence will not be initiated.

Registering (programming) new keys is the most common issue with this system. It’s usually easy and it can be done with aftermarket pass-through tools. Once you’re in the right section of the Toyota Information System (TIS) website, the process is menu-driven and takes only a few minutes. You can register new keys or keys that had previously been used in another vehicle. However, if you only have a valet key and not a master key, you’ll need a locksmith identification number (LSID). It’s also easy for key registration to fail. Toyota notes that only one key should be in the car during key registration: If there’s more than one, they will interfere with each other and prevent the process from running to completion.

The key registration process was updated last year (July 2014). Toyota Service Bulletin 0043-14 describes new security requirements to obtain a smart key reset pass-code, and the instructions for this new process must be reviewed before attempting to get the pass-code. The TSB also describes how to reset a vehicle immobilizer and/or smart key system.

Service bulletins

Since we’re on the subject of TSBs, don’t forget there were many bulletins and recalls to address accelerator pedal issues on all Toyota models. Here are some of the other important service bulletins covering the fifth and sixth generation Camry.

TSB-0122-08 describes why some smart keys tend to use up their battery quickly. The smart key “wakes up” upon receiving a “ping” or query signal from the BCM, but other electronic devices also emit signals that may activate the smart key. These include certain video devices, computers and monitors, cell phones and cordless telephones, microwave ovens and even some light fixtures. The only fix is to keep the smart key at least three feet away from other electronic devices.

TSB-0003-09 says a faulty “Engine Start” button may cause intermittent no crank/no start on vehicles with smart key. The bulletin describes a diagnostic procedure and includes part numbers for replacement buttons.

Service Campaign SC90K was launched to replace the oil supply line for the camshaft actuator on the six-cylinder engine. The rubber part of that line can develop a leak big enough to turn on the oil pressure light. Parts or repairs are free if the work is performed at a Toyota dealer before the end of 2021(no mention of reimbursement for work done elsewhere).

Safety Recall SC-C0M130213-007 was issued to cover all 2007–2009 Toyota models, but not all VINs (the National Highway Traffic Safety Administration (NHTSA) recall number is 12V491000). The master power window switch tends to stick or develop a “notchy” feeling over time. If that switch is lubricated with “commercially available” lubricants, it may overheat and melt or even catch fire (evidently there were lubrication “irregularities” at the factory). The recall bulletin describes how to disassemble, lube and reassemble the switch using the special grease (04002-18242) and applicator syringe. You’ll need some new one-way screws (04002-18342) to reassemble the switch.

The next generation Camry has even more changes, including a new 2.5-liter engine and lots of new electronic features on the control screen. It will be a while before these models appear in your service bay, but it’s never too early to start learning about them.   ‚óŹ

Thank you to the technicians at MotoLOGIC for their help in preparing this article. –Ed.

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