I've had the Service Engine Soon light on in my truck for a bit. In the past, I had found a P0113, Intake Air Temperature Circuit High. Recently, I found the following codes when plugging in the Snap-On scanner from the shop.


P0113 : IAT circuit high


P0236 : Turbo Boost Sensor 1 Out of Range


P0717 : No/low input turbine speed sensor SI


P1871 : Undefined gear ratio


For the P0113 code, I discovered the problem to be a bad connector. Playing with the wires to the connector intermittantly causes the IAT temperature to drop to -38 F from a proper reading (~75-80 degrees while sitting engine off on a 70 degree day). For the P0236 I assume that I should start by checking the MAP sensor (reads a proper 106 kPa when sitting engine off, and it goes up to about 140 kPa when flooring it. Haven't tried playing with the connector on it. The P0717 I have no clue what to make of or what to look at for.


The P1871 I believe was caused when I put in an alternator rebuilt by an independent shop. They put a smaller pulley on it, and I then noticed that my revs were reading higher on the tach. So that probably did it.


Any ideas on the P0236 and the P0717 codes? Thanks for the help!

I would think another bad connection. My boostjacker popped the soder off a mapwire to switch connection and I got the boost out of range code.

The 4L80E has two speed sensors - input turbine speed and output speed.


PCM uses these for various functions, including which gear the trans is in.


P0717 indicates PCM is not reading the input sensor frequency


P1871 indicates PCM cannot define gear ratio due to no input-to-output frequency comparison


PCM reads engine rpm off Crank Position Sensor, compares this to input turbine sensor for torque convertor slip ratio, and is compared to output sensor for gear ratio.


Probably loose connections in transmission harness.


P0236 is probably loose connection to Boost Sensor - this DTC is result of input measurement taken before engine starts, ensuring base reference is correct


Low DTC usually means open signal wire or loose connection.


Hi DTC is open ground wire, signal wire shorted to power wiring, or failed sensor Edited by: gmctd