Been getting 2 codes
1) IAT LO
2) MAP Hi


Been having a intermitant IAT LO for the past couple of seasons. Every time I put the volt meter on the plug I'm getting the correct voltage... I ohm out the IAT and its fine. Even have confirmed 0 ohms between the ecm and the IAT sensor. The wires read out fine. Even tried a seperate ground wire to the IAT. I still have the intermintant problem. This should be pretty straight forward but what else could it be?

Map Hi, I'm still looking into that

 

IAT Lo is most likely an intermittent sensor. Or an intermittent wire or connector. Low temperature is read with an open circuit.

MAP High is easily caused by an engine that isn't running right. Basically, TPS is at a low value and the MAP reads high, within a certain RPM.

An engine that has trouble running, as in not quite tuned in yet, will exhibit a high MAP error.

If it is due to a radically cam'd engine, increased this value:

MALF33 - MAP Hi BARO Limit (nbar)

Of course do need to check the vacuum line between the plenum and MAP sensor. That too will cause a malf 33.

RBob.

 

For now I'm not gonna worry a lot about the malf 33. I'm thinking the same thing as you. BTW right now my MALF33 HI BARO LIMIT is set to 67.98..should that be higher?

Even before this engine change I've always had the issue with the IAT sensor. Changed it to new ones last year 3 times. Everytime I test and test and everything from the sensor back to the ecm tests fine.

I'm starting to wonder if its the type of IAT I'm using. Presently I use the MAT/CTS sensor. I found that thread about this and read through it. I'm thinking of trying the air temperture sensor from a 92 GMC typhoon. It fits the connector I already have. After reading through the other thread will I have to make changes to the MAT/CTS blend filter table?

 

You can increase the 68 KPa limit. I usually set it to 10 KPa higher then what the idle MAP KPa is. So if it idles at 60 KPa, set it to 70 KPa.

IAT: it may be either the connector for the IAT is bad, or the terminal/pin at the ECM. A bad ground for it will also cause this malf code.

RBob.

 

On a cold idle I'm at 60-70kpa so I'll make that adjustment to see what happens.

I also picked up a true IAT sensor for a 95 Impala SS. I temporarily plugged it in and its reading the correct temperature. I'm gonna try that and see what happens.

 

Just about had it with this IAT code.
Its a simple circuit +5 volt wire and a ground wire, sensor and connector.
I'm now on my 5th sensor and connector. Wires from the ECM are perfectly fine and have been read out using a DVM, both for voltage and ohm. Same for the sensors they have been ohm'd out cold and hot. All test fine.
That only leaves the ecm. Opened it up to check the solder joints from the HAM board to the EBL flash board. Solder joint appears fine.
WTH can this be?

I believe that if my IAT is showing a code 23 the car is gonna run like crap..which it is.