Cdeez

Well my most recent TBI tuning saga continues. Tonight, for no apparent reason after chasing my tail a while on the VE table, flow rate and AE tables, the MAP sensor stopped reporting in the datastream... It's locked at 54 some KPA.... No error codes.....

Any ideas?

ULTM8Z

I guess first I'd try rebooting TP and see if the problem corrects itself. Could just be some sort of glitch. I've had it on occasion where TP just freezes during a run and I have to shut it down and restart it.

I'd also then verify the output of the MAP sensor itself... back probe the ECM at the MAP sensor connections to ensure the ECM is getting the right output from the sensor.

Cdeez

Thanks ULTM8Z. I have rebooted TP and the laptop several times with no result. Also replaced my ADX thinking that maybe it got corrupted or something but that didn't work either.

I'm having trouble finding the correct procedure for testing the MAP itself as well as the circuits? I've found some that involve a Tech 2 or whatever scan tool but all I have is a multimeter.

Cdeez

And randomly the MAP sensor is reporting in the datastream again. I unplugged and plugged the ALDL connector back in. Could it really have been that simple?

Cdeez

While driving around and still working on figuring out what fueling this thing likes I'm still dealing with an intermittent lean pop in some of the middle to upper VE cells it seems. When this happens it SEEMS that it causes the MAP sensor to LOCK in midrange, about 50 to 55 KPA or so and it STAYS locked there for a time that is random and un-repeatable.

Is there a setting that might be causing this? Any thoughts?

ULTM8Z

THere are youtube videos on how to test the MAP sensor.

such as this one...


what you can do when the MAP sensor "locks" is take the multimeter to it while still hooked up to the harness and with the key on (engine off) and see if you're getting the ~4.5V indicative of atmospheric pressure, or if you're getting something on hte order of 2-3V, indicative of ~50 kPA, in which case, check the TP data again and if the multimeter and TP agreee, then there's something wrong with the sensor. TP will read and report the sensor with the engine off.

If you get 4.5V on the multimeter, and TP is saying it's 50kPa, then there's something wrong besides the sensor.... harness wiring, ADX file, etc...

Lastly what you can do (if TP has this) is to display the MAP sensor volts rather than the calculated pressure. If the volts readout in TP doesn't remain locked, then there's something going within TP.

Cdeez

Thanks! I will look into this.

Cdeez

ULTM8Z,

Thanks for pointing me in the right direction. Sure enough, the MAP sensor had failed. Tested it like you described and used that video as well. Got 2 other MAP sensors from some other TBI trucks and swapped them around while monitoring the multimeter as well as TP..... All is good, for now.

ULTM8Z

cool... glad it worked out.

Cdeez

Figure out why the MAP wasn't working. The conformal coating inside was soft as jello. Looks like it even plugged up the hole where the vacuum port is.