Not A Crank Sensor
I am posting this as a Tech Tip in hopes that it will save time in diagnosing and to avoid an improper diagnosis. For those that have not encountered this, pay attention!!! For most of us in the business, if a customer complained of a Crank No Start condition accompanied by a loss of an RPM signal, collectively we would all agree by guessing that they need a Crank Sensor. But WAIT... we don't guess here! The majority of the diagnosis was spent on the computer reading, researching and understanding the system that I am working with. Understand how the system works and you will understand why it fails.
Here we go... after reporting my rushed findings to the service manager, he said "ok, so we need a crank sensor..." I said, seems possible but not sure at this point. He estimated a Timing Belt/Water Pump job w/Crank Sensor and scheduled it with the customer. He saw I was not comfortable with this and scheduled time for additional checking before carrying out the job. Customer returned and eventually during the day I pulled the vehicle in. Now that I was armed with close to an hour of thorough reading on the system, it was clear to me that:
- The Crank Sensor does NOT control the tachometer but WILL send an RPM signal via the computer to the RPM counter on the scanner
- If you have no crank signal, obviously no fuel and spark timing means the vehicle will not run (at the time the tachometer was NOT working while at idle in the shop I immediately ruled out a crank sensor for that issue)
- The Ignition Failure Sensor (IFS) is used to check whether the spark ignition has occurred correctly or not and also used to drive the tachometer.
To the point... visual inspection... knowing that the power draw of the coil runs through the IFS, I randomly felt the coil tops for excessive heat. What I found, was a hard and definitive ignition spark pulsating through the coil and the attached wire. I checked for a loose plug in that cylinder. All was well. I switch the coils and the ignition pulse followed the coil. Out of curiosity I felt the IFS and it was quite warm. I wiggled the harness and walked around the side of the vehicle and suddenly PRESTO the tachometer was working! I had another tech come over and assist viewing the tachometer while I continued the wiggle test. SURE ENOUGH, the tachometer would drop out under certain sensor pressures. My conclusion was the spark was literally bouncing around inside the coil vs a direct path and excessive amperage draw to fire this coil and push the spark damaged the IFS...
Don't guess... don't be a parts changer... do right for the customer!!!
I missed the only Hyundai class (ever) around here, several years ago, but was able to borrow a book later. It is indeed a unique system that has the IFS driving the tach. I also did a one year subscription to the Standard Motors online training. There is a "tips and tricks" series there, that has the unique need-to-know facts about many popular OE brands. They cover the Hyundai IFS,
Thanks for the write-up!
When I read that name (Ignition Failure Sensor) it struck something in my memory about a vehicle I had repaired in 2010. It was a 05 HYUNDAI XG350L 3.5L V6 VIN KMHFU45E55A385434 that was giving a P0320 Active Ignition/Distributor Engine Speed Input Circuit and the tachometer was not working. Replacing the Ignition Failure Sensor fixed the code and the tachometer operation.
Thanks for the reminder.