JyRO

Guys,

My truck has been running fine. But I on-off'd the ignition to check the codes anyway, and got the ole P1693 companion code. Took the truck to a buddy's house who has a big fancy code scanner, and he pulled up the P0236.

The code means: MAP Sensor Too High Too Long.

His code scanner would also show real time sensor activity, so we recorded the MAP sensor readings 4 times. The highest it would read was 4.1 in.Hg. That converts to ~2 p.s.i. I purposely tried to & could hear the truck over-boosting (EZ with elbow) during those 4 recorded events.

I've read some of the searches about P0236, and I have a theory. I'll need to hook up to his code scanner one more time to confirm, unless you guys already know this (which I'm sure a few guys will know).

Theory: My overboosting has damaged the MAP sensor (since it was designed to read up to ~21 p.s.i. The result is that now the MAP sensor always reads ~5V (too high too long). This is assuming (this is where you guys kick in) that the MAP sensor voltage, and the boost pressure are inverse to each other. Meaning at 0 boost, the MAP sensor voltage is at max ... 5V. When the boost is at max, the MAP sensor voltage is ~0 psi.

Basically, what it boils down to is, I think I should replace my map sensor. But I'm also confused, because the truck seems to run just fine. Does anyone agree? And anyone know about how much a MAP sensor costs? Any other thoughts? Thanks.

- JyRO

phox_mulder

EZ has a built in boost fooler, so what the scanner is seeing is the same false signal that the ECM is seeing, what the EZ is sending.

Try disconnecting the EZ and see what the real time readings are.


phox

JyRO

Is this true? I thought the MAP sensor reading is what the boost fooler was manipulating before the overboost signal got to the ECM. For instance, the MAP sensor says 15 psi, the boost fooler does nothing. The MAP sensor says 25 psi, the boost sensor steps in and fools / manipulates the sensor signal to the ECM into saying the boost is 21 psi (or whatever max boost is).

I could understand being able to read the MAP sensor and see an overboost condition. But thought that MAP signal was changed by the boost fooler when the signal is indicating overboost.

- JyRO

CTD NUT

P0238 MAP Sensor Voltage Too High

That is the DTC for the MAP voltage being too high. This is an out of range condition as is P0237 (MAP Sensor Voltage Too Low).

P0236 Turbocharger Boost Sensor A Circuit Range/Performance

0236 is representitive of a skewed sensor. Which means it could be operating erratically or not at all.

This is all hypothetical....since you already have easy access to the tool that will measure MAP voltage during operating conditions, just measure the voltage. Regardless, it is most likely that the MAP as packed it in since that is the DTC it throws when it dies. Don't forget to unplug the EZ as Phox mentioned to take it out of the loop so as to better isolate the MAP voltage. Also, clear the 0236 DTC and unplug the EZ and see if the 0236 returns.....if it does, the MAP is toast.....if it doesn't, maybe there could be a potential problem with the EZ?

As to the theory that the excess boost causes damage to the MAP because it is running out of it's intended voltage range, I have never heard that. What is it's intended range? The MAP range and engine boost limit are not related in any kind of way. There are many ISB applications that run more than 21 psi of boost with the exact same MAP sensor. Also, you will notice that the 0234 overboost DTC does NOT throw an additional 0236, 0237 or 0238 when the engine exceeds it's set boost limit which would lead one to conclude that an engine overboost condition is not related to any type of MAP voltage out of range condition, improper circuit voltage or a skewed or non functioning MAP. My point is that there is no evidence to suggest that a MAP seeing more than 21 psi is being damaged or operating out of it's range. There are many CTD's that have been running for years with manipulated boost signals and much higher than stock boost levels with literally no issues at all with the MAP sensor.

JyRO

CTD NUT - I see your point here. It makes sense. My point was not running the voltage out of its parameter, but that the increased boost pressure may actually be causing some physical damage to the MAP sensor. But you're right. I'm blowing sissy boost compared to a lot of guys. There'd be MAP sensors going left and right if my theory was the case. So I'm going to do as you suggest on here and pull the EZ, and see what happens. How much is a MAP sensor anyway? Later.

- JyRO

phox_mulder

Yes, I think that's what I said

Could be as simple as a dirty connection between the MAP sensor and the EZ, or the EZ and the MAP plug (to the ECM).


phox

JyRO

phox - You know what, its been a long time since I connected the EZ, but I do remember having to fish it around in place to push it in. Could be I got some dirt in there, but its just now causing a problem. I'll get this figured out, hopefully have time to work on it this weekend.