I have a 93 Sol w/H22 (on chipped P28 with a stock H22 rom), and I was replacing my brake booster/MC two weeks ago. If you're familiar with this hybrid, there isn't much space around the intake manifold, and the new BB was hanging up on the IAT sensor. I tried to remove it, but one of the screws was siezed. One of my friends tried and stripped it, so I grabbed a hammer and broke the sensor. I sealed up the hole on the IM and finished my brakes. The car idled normally (no vacuum leak) with a cel. Since I had been cel free for at least 6 months, and had just destroyed a sensor, I assumed it was IAT and started my search for a new sensor. One of my friends had one from his old single cam (that he says was cel free when he pulled the motor a year ago) that was sitting on a shelf in his garage. The sensor looked to be in good shape, so I installed it, reset the ecu and started the car. The cel was still there. So now I pull the code. 7 short flashes... TPS (IAT is 10), wtf? I traced all the wires for TPS and IAT, and all connections are good and in the correct pinout (used multimeter too). I unplug the IAT sensor, reset the ecu again, get the cel, pull the code, and still only 7. I thought maybe I need to drive more for the ecu to recognize that IAT is missing, so I drive around normally for 2 days, check the cel, still only 7. My car drives great, no reason to suspect any tps problems, and if I unplugged IAT, why wouldn't it throw code 10? Has anything similar happened to anyone else? WTF is going on? Thanks for reading the entire problem.

 

Bump because I have no idea what the cause is. Does the IAT reading need to be within a range of the TPS or something? I took my ecu apart to look at the board, and nothing looks/smells fried. That was the only idea I could come up with. If any part of this problem makes sense to someone, please let me know. I really hope i'm not the unlucky first person on h-t to have this problem.

 

I just re-wired both of these sensors manually in my car (directly from the sensor to the ECU). I am not sure what's causing your problems, but in my case re-wiring fixed the problem (I was getting codes for IAT, TPS and ECT most likely because of a bad engine harness).

Not sure about the reading on the IAT, but the TPS sensor should range from .5V at idle to to 5V at WOT. Try to test that with the multi-meter (you will probably need another person to hold it for you while you simulate movement with the TPS sensor, and see if it will give you the right reading.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dynamo &raquo;</TD></TR><TR><TD CLASS="quote">Not sure about the reading on the IAT, but the TPS sensor should range from .5V at idle to to 5V at WOT. Try to test that with the multi-meter (you will probably need another person to hold it for you while you simulate movement with the TPS sensor, and see if it will give you the right reading.</TD></TR></TABLE>

The voltage is correct for TPS. I checked that last night. Thanks for the reply . I think I'm going to take a real close look at the board of my ecu tonight. I've been over the wiring at least 10 times now, and the voltage is correct, so I'm gonna start looking for missing resistors or capacitors on the board.

 

Why don't you borrow a working ECU from someone and just plug it in to see if it works? Might be more accurate (and easier) than taking apart yours.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by dynamo &raquo;</TD></TR><TR><TD CLASS="quote">Why don't you borrow a working ECU from someone and just plug it in to see if it works? Might be more accurate (and easier) than taking apart yours.</TD></TR></TABLE>

thought about that, but I don't know anyone with an obd1 p13, chipped p28, or p72. Anyone who had an ecu I could use has sold their car. Maybe its time I do the same... I'll figure it out eventually, I was just hoping that someone else has solved this problem before.

 

Where you measure the voltage for the TPS at? At the sensor or at the ECU?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turbogixxer &raquo;</TD></TR><TR><TD CLASS="quote">Where you measure the voltage for the TPS at? At the sensor or at the ECU?</TD></TR></TABLE>

at the harness where the ecu plugs in.

 

Ok, one of my tps wires was grounding out to the firewall intermittently. That explains the cel, and I guess it just wasn't grounded at the moment I checked the wires with a multimeter. So that's fixed now, and I no longer have a cel, even without my IAT plugged in. So now that's the weird part. Apparently my ecu isn't looking for IAT. Weird...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by IHateJDM &raquo;</TD></TR><TR><TD CLASS="quote">Ok, one of my tps wires was grounding out to the firewall intermittently. That explains the cel, and I guess it just wasn't grounded at the moment I checked the wires with a multimeter. So that's fixed now, and I no longer have a cel, even without my IAT plugged in. So now that's the weird part. Apparently my ecu isn't looking for IAT. Weird...</TD></TR></TABLE>

that was a wierd problem. Glad to hear it's fixed

 

Good catch - how did you figure out that it was grounding out?

 

the hard way, traced every inch of each wire til i found it. Has anyone else ever run without IAT and no cel before?

 

Not that I know of.... Have you tried to measure and see if the ECU is getting the correct voltage when the car is running? Voltage specs should be in the Helms.

 

My iat is unplugged and the wires are not hooked up at all, so the voltage is 0, and still no cel.