Auto Service Professional

DEC 2018

Magazine for the auto service professional

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18 A S P D e c e m b e r 2 018 T e c h s H e l p i n g T e c h s flow through the engine, reducing cooling sys- tem pressure and better regulating temperature variations in the engine block. When the coolant reaches 180 degrees F (82 degrees C) the thermostat will open and allow coolant to flow to the radiator. e PCM can vary the temperature of the coolant coming in contact with the thermostat by using the cool- ant bypass solenoid. is results in a variable operating temperature zone of between 180 de- grees F (82 degrees C) and 198 degrees F (92 de- grees C). is allows higher operating tempera- ture during part throttle resulting in increased fuel economy. Both of these aforementioned solenoids can set trouble codes for circuit diagnostics and electrical faults. e standard thermostat codes P0128 and P0125 can easily be due to a faulty wax pellet thermostat, as well as a low coolant level. As memory serves, Ford did have a recall on some of these engines for a failure of the by- pass valve that accidentally allowed the engine to overheat. Jeff Taylor Eccles Automotive CRANK BUT NO-START When beginning to diagnose a crank-no-start condition, here's a tip that can help you isolate the problem. You already know that when a cylinder mis- fires continuously, the PCM will turn off the dead cylinder's injector to avoid sending gasoline straight into the catalytic converter. However, it doesn't remember the misfire, as it discovers the misfire anew each time the engine is started. So the PCM will operate the injector during crank- ing and for a short period right aer start-up un- til it knows for sure the cylinder isn't firing. If you're watching the injectors on a "scope" and they all operate during the first 200 engine revolutions at start-up, the injectors are OK. Jim Gates Gates Auto CAMRY SMART KEY e sixth generation Toyota Camry is the first avail- able with an optional Smart Key system that has an Engine Start button in place of an ignition key. e 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). e 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 En- gine 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 but- ton is pressed with the gear selector in Park or Neutral and the brake pedal depressed, the BCM activates both ignition relays, unlocks the steer- ing and sends a "start" request to the PCM. e PCM will then request a cut in accessory power (from the BCM) while it activates the starter re- lay. Once engine speed reaches 1,200 rpm, it will release the starter relay and terminate the acces- sory-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 sec- onds. If there is no fuel in the tank (or if the fuel gauge sending unit fails), the start sequence will not be initiated. Bobby Young Bobby Y Service HONDA ELECTRIC POWER STEERING ere are a few known issues on the Fit, Civic and Insight. e steering racks are built lighter and are more compact than hydraulic units, so the rack fits into smaller spaces. Unfortunately, this makes it a bit more susceptible to collision damage. Since there is no hydraulic fluid, a cracked housing is not always obvious. In fact, Honda techs and collision repair shops have reported that steering rack damage can't be seen with the rack mounted in the car. Also unfortunately, on most models, the subframe must be removed in order to remove the EPS steering rack. Fortunately though, the control unit is in- side the vehicle, usually under the right side of

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