Ok, I have to admit this is the first time I ran into a problem like this.. For some reason, I got a CEL for code 10 through s300. As soon as you turn on the car, the CEL just stays on and doesnt blink like it usual. I did all the test from checking voltage from the red/yellow wire which im getting 5v from, and the other wire green/white for ground. I did a continuity test on both wires from the plug to ecu, and im getting no resistance from both wires at all. I swapped at least 3-4 ecu i had laying around and its still doing the same thing. I followed the IAT troubleshoot via service manual i found online. Im so stumped, its aggravating the crap out of me, can somebody please help me out!

 

 

Nothing? Cmon somebody please help me out!

 

The grn-white is +5 volt sensor power from the ECU. It goes in parallel to several other sensors such as MAP, TPS, and ECT.

The red-yel is the sensor output, it should be something less than 5 volts and increase with temperature.

Unplug ECU with sensors still plugged in, and measure sensor resistance all the way through the wires from the ECU plugs.

It is OBD1? Can you do a simple blink code check? Of course if there are no codes and the test jumper is in, CEL will stay on steady whether engine is running or not.

 

Ill check for resistance in the wires again when I get home.. Another problem is that I never did the test jumper to have it blink.. I used the laptop to see what the check engine light was on for... I tested resistance from the green/white wire on the IAT to D22 ecu side. The car is a 94 civic so its an obd1...

 

Follow the Helm manual troubleshooting and test the sensor. If there is resistance across it it is likely okay, they usually fail open and I have never heard of or seen one fail shorted. Are you saying you have no resistance between the red/yellow and green/white with the sensor unplugged? That would indicate that your sensor wire (red/yellow) is shorted to ground somewhere.

Here's my contribution to charity for the day :

 

Ok finally solved the damn problem! The IAT, I had gave resistance readings on the sensor at first.. When i continued to do a little more testing, like heating it up just to see if it would change, it ended showing no resistance between the terminals on the sensor at all.. So bought a new sensor from Vatozone and now CEL is gone! Thanks for the hell guys!