Domestic Driveability Diagnostics & Tips
Sponsored By NGK Spark Plugs
Learn how to streamline the diagnostic process for driveability issues. This webinar will help you effectively communicate a vehicle diagnosis to the service advisor. The presentation will provide "real-world" data and cases studies.
This technical topic is geared for the average B+ technician and/or a refresher for the A technician. NGK is dedicated to meeting the learning needs of all skill levels.
Speakers Philip Austin, Technical Training Specialist, NGK Spark Plugs Andrew Markel, Director of Technical Content, ShopOwner
Sponsored By NGK Spark Plugs
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Brake & Front End serves repair shops conducting a high volume of undercar repairs by providing application-specific technical information and solutions to address emerging trends in the undercar repair segment. By subscribing, you’ll receive the ShopOwner digital edition magazine (12 times/year) featuring articles from Brake & Front End and the Brake & Front End eNewsletter (twice weekly). Access to digital editions, contests, news, and more are ready for you today!
Brake & Front End serves repair shops conducting a high volume of undercar repairs by providing application-specific technical information and solutions to address emerging trends in the undercar repair segment. By subscribing, you’ll receive the ShopOwner digital edition magazine (12 times/year) featuring articles from Brake & Front End and the Brake & Front End eNewsletter (twice weekly). Access to digital editions, contests, news, and more are ready for you today!
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Does performing a pad replacement on a Toyota Prius scare you? Well it should; if you treat it like every other vehicle. But, if you know a few things ahead of time, the job can be performed like any other brake job.
Do not worry about high voltage. Worry about angry customers due to comebacks because the brake/ABS light is on. Servicing a Prius does not require many special tools to perform a front brake pad replacement. Just normal hand tools are required and maybe a scan tool and software that can read chassis codes if you are unlucky or have to replace hydraulic components. But, it is possible, according to Toyota, to replace pads without a scan tool.
There are three basic concepts that technicians must be aware of before they push back the pistons on the front calipers. First, the most important basic aspect to grasp for any technician is that the Prius braking system has pressure sensors at the master cylinder and the outputs for wheels. These sensors check the pressure and any anomalies between the two pressures will cause a trouble code to be set.
Second, when the driver is pushing on the brake pedal, it might not be producing hydraulic braking force at the wheel. The system is measuring the stroke and pressure generated at the brake pedal and translating that into braking force created by a generator. The system is not a full-time brake-by-wire system. Hydraulic brakes are used during hard stops and at speeds below 10 mph. When the regenerative braking is engaged, it will give the driver feedback with a device called the “stroke simulator.”
Last, even if the engine is off and the car is not moving, there is still hydraulic pressure in some of the lines. The Prius can drive without the internal combustion engine running. Also, even if the car is in park without the engine running and the keys in the ignition, the engine may start to charge the battery or run the HVAC system. The keys need to be out and away from the vehicle during service. If you keep these concepts in the back of your mind, you should be able to perform any brake service with the right tools.
Prius Models The Prius was introduced in 2001. The rotor and caliper are the same as the Echo, Scion Xa/Xb and MR2. In 2004, Toyota changed the brake system when it upgraded the batteries and electric motor. The most distinctive difference is the lack of a vacuum brake booster. In 2004, a different ECU and larger accumulator and pump now provided the boost.
At the wheel, the system stayed the same in regard to the rotor and caliper. But, the brake pad characteristics were changed for better longevity and corrosion resistance.
At the rear are drum brakes without any regenerative braking. The rear drum brake is almost bullet-proof. But, there have been some problems with the emergency/parking brake cables and the electric motor that actuates the system. In TSB BR002-07, it outlines how to resolve problems with the brake light staying illuminated after the emergency/parking brake has been disengaged. This procedure will require a scan tool
The Pads It is not uncommon to find a Prius with 70,000- or 100,000-miles with the original set of pads. This is due to regenerative braking creating the majority of braking force. But, this does not mean that other components, like hardware and rubber seals/boots, can’t fail sooner.
The Prius has unique requirements for the brake system. On 2001-2004 models, the hydraulic brakes were not used until the vehicle was below 7 mph or if the vehicle had to make a hard stop.
The majority of the time, the pads never reached conventional operating temperatures and corrosion could occur between the backing plate and friction material due to the fact that the pads never dried out. On some vehicles, the corrosion between the friction material and backing plate would cause a complete separation.
Always use a high-quality pad for the Prius and other hybrid applications to avoid problems. It is not a question of better performance. It is a question of quality and engineering.
Since it is impossible to perform a conventional break-in/bedding procedure on the test drive, make sure the manufacturer promises excellent performance right out of the box. Also, applying a non-direction finish with a ball hone will help the new pads evenly deposit a layer of friction material to the new rotor.
The Prius use a two-part shim. The solid piece is the anti-noise layer. The perforated part provides lubrication and acts as a bearing. The two shims’ contact areas float on the lube and slide during application. Always replace the shim and do not reuse an old shim!
Rotors There is nothing special about servicing the rotors on this vehicle. But, if you are planning to use an on-the-car brake lathe, make sure the system is off for two minutes. Most on-the-car brake lathes operate below the speed threshold of the generator’s ability to generate voltage.
Rotors that have excessive runout or thickness variation can cause hydraulic pulsations in the brake circuit. These irregularities can cause the pressure sensor to trigger trouble codes C1341 thru C1344 that indicate a hydraulic circuit malfunction.
Hydraulic Components If you have to replace a caliper, wheel cylinder or brake hose, you must have a scan tool that can clear codes and operate the ABS pump during bleeding. Manual or “one man” bleeding will not work on this vehicle due to the valves and solenoids that manage the regenerative braking. Also, the system must be deactivated to prevent damage the components. Also, read all of the precautions in the service information before attempting to replace any hydraulic component.
If you are replacing calipers or other hydraulic components, you will have to deactivate the system with a scan tool. Most scan tools will walk you through the process that involves removing the two ABS pump relays and pumping the pedal in a sequence to depressurize the system. The system can also be deactivated by waiting for two minutes after turning the power switch OFF, stopping the brake pedal operation and closing the driver door before removing the two relays (see photo).
Also, it is a good practice when working on vehicles with advanced ABS and Stability Control systems to remove the keys from the vehicle and place in a different room, like at the front counter.
Do not use excessive amounts of grease that can contaminate the friction material once the brakes have been heated.
ABS Light On? If the ABS light did come on during the test drive, disconnecting the battery is not the way to clear the codes. Yes, it will clear some codes, but you will have to recalibrate the steering position sensor and other items, like the automatic power windows, will stop functioning.
What happened during the test drive is that the pressure sensors at the wheel detected an abnormal reading when the hydraulic system was first engaged. The system may have detected low pressure when extra fluid is required to bring the piston into contact with the rotor, or residual pressure from you pushing the piston back. DTCs may be stored if brake fluid leaks, wheel cylinder vibrates due to uneven wear of the brake disc rotor, or foreign matter enters the solenoid valve.
Toyota has issued a Technical Service Bulletin BR012-06 on the topic. It states: “When replacing the brake pads on an ECB (Electronically Controlled Brake) system equipped vehicle, retracting the caliper’s piston and installing new brake pads may cause trouble codes to set the next time the brake pedal is depressed.”
If any of the following four trouble codes are set, all the codes need to be cleared and another test drive completed to verify the code has been cleared:
If you do not have a scan tool, it is possible to clear the codes with Special Service Tool (SST) 09843-18040 (Basically a fancy jumper wire).
(a) Using SST, connect terminals TC and CG of the DLC3.
(b) Turn the power switch ON (READY).
(c) Clear the DTCs stored in the ECU by depressing the brake pedal eight times or more within five seconds.
(d) Check that the warning light indicates a normal system code.
Note: Clearing the DTCs cannot be performed by removing the cable from the negative (-) battery terminal or the ECU-IG fuse.
Conclusion In May 2008, Toyota announced that its worldwide cumulative sales of the Prius had passed the 1 million mark. Nearly 60% of all Prius sales have been in North America where 183,800 vehicles were sold in 2007. This is a significant opportunity for shops as the age of the hybrid fleet starts to age.
You will not have to wear insulated gloves and use rubber-coated tools to work on the brake system, but you will have to arm yourself with knowledge.
PRIUS TSBs TSB BR002-07: Parking Brake Warning Light stays illuminated after the parking brake pedal is released.
Models: 2004 –2007 Prius Some 2004 – 2007 model year Prius vehicle customers may complain that the Parking Brake Warning Light stays illuminated after the parking brake pedal is released. The parking brake assembly, which includes the parking brake switch, has been modified to correct this condition. Use the following repair procedure to remove and replace the parking brake pedal assembly.
(Includes 2004 – 2007 model year Prius vehicles produced BEFORE the production change effective on VINs JTDKB20U#73249043 thru JTDKB20U#77632091.)
TSB BR002-07: Brake Actuator Noise Covers: 2004 – 2007 Prius Some 2004 – 2007 model year Prius vehicles may exhibit a squeak-type noise when pressing or releasing the brake pedal. This noise may only be audible when the vehicle is in “READY” mode and the vehicle is not moving. Brake system performance is not affected by this noise. Use the following procedure to address this concern.
Refer to your source of repair information for the correct procedure.
4. Road test for proper operation.
Wheel End: Composite Brake Rotor Service Opportunities
Wheel End: Proper Alignment is Critical to ADAS Operation
Wheel End: How Regenerative Brakes Operate
Wheel End: CV Joint Replacement Tips
Technical Resources for diagnosing and servicing undercar components