P0717 is a somewhat rare OBD2 trouble code that can occur in the Chevy Blazer. While it illuminates the check engine light, the code warns of a transmission-related error, specifically that the input shaft/turbine speed sensor is not sending a signal.
P0717 is a generic code (it has the same meaning for any vehicle made for the 1996 model year and up).
P0717 Definition: Input/Turbine Speed Sensor – “A” Circuit No Signal
Here is the meaning of P0717 broken down by its two main parts.
Input/Turbine Speed Sensor
Your Blazer’s input/turbine speed sensor measures the speed of the input shaft. It does this by using a reluctor wheel and magnets (magnets go on the sensor tip)
The reluctor wheel will have notches cut into it. As the input shaft turns, the input/turbine speed sensor can tell each time one of these notches passes it.
It relays this data to your Blazer’s PCM/TCM, which determines input shaft speed. At this point, the PCM compares this data to engine RPM, the output shaft speed sensor, and the vehicle’s speed.
The input speed sensor is usually screwed into or bolted onto the transmission. It’ll be close to the bellhousing since it measures how fast the torque converter is spinning.
“A” Circuit No Signal
With P0717, there is no voltage coming from the input/turbine speed sensor. If the loss of voltage were intermittent, P0715 would be the code.
P0717 Symptoms: Chevy Blazer
Here are the most common symptoms associated with P0717 in the Chevy Blazer:
- Torque converter not locking
- Transmission enters limp mode
- The speedometer doesn’t function properly
- Hard shifting
- The transmission doesn’t shift at the normal RPM
Depending on the transmission in question, the symptoms can range from inconvenient to undrivable.
Chevy Blazer P0717 Causes + Diagnosis
The good news is with P0717 there aren’t a lot of common causes, and the fix is usually pretty straightforward. Here’s how to go about diagnosing this code in your Blazer:
1. Check the Wiring Harness (Likely)
The wiring harness is going to be where you would want to start looking for P0717’s causes. Check for damaged wiring, particularly where the harness plugs into the input/turbine speed sensor.
Do the pins look corrosion-free? They may need cleaning to make good contact. Use an electrical contact cleaner.
Verify that the ground is solid. If there doesn’t look to be any visible damage, you can verify the voltage with a voltmeter.
Repair the wiring harness as needed.
2. Input Speed Sensor (Very Likely)
Now that you have verified that the wiring going to the input/turbine speed sensor is functioning, it’s likely that the sensor itself is malfunctioning and causing P0717 in your Blazer.
If you pull the sensor, verify that there are no metal shavings on its magnetic tip. If there are, that can be enough to disrupt the signal. You can try cleaning the shavings off and seeing if the sensor begins to function again.
Use a voltmeter to test voltage going in and out of the sensor. Otherwise, you may end up replacing a sensor that is still working fine.
Pull this sensor when the transmission is cool to avoid getting burning hot ATF on yourself.
3. PCM (Not Very Likely)
It’s possible that the PCM can be at fault. Only suspect it if the sensor and wiring appeared to be just fine. Verify that there are no technical service bulletins relating to the PCM from Chevy.
While it’s hard to drive your Chevy Blazer with P0717, fixing it is relatively straightforward. Good luck!