Gray smoke
09-21-2003, 03:29 PM
#31
Registered User
Join Date: Apr 2002
Posts: 1,135
Likes: 0
Received 0 Likes
on
0 Posts
Re:Gray smoke
The 14 psi was my mistake. Memory isn't as good as it used to be. I went back and looked at a log file I have of my OBD2 readout.
It reads the same with or without a box connected.
It reads the same with or without a box connected.
09-21-2003, 03:43 PM
#32
Registered User
Re:Gray smoke
Now it gets rather interesting. So you do read a higher than athmospheric pressure with just the key on? Did you see this on other trucks too or is yours the only one reading this value?
The reason I ask is that I didn't get my hands on an 01 yet, but this could be very interesting to know before throwing MAP sensors on one that may have a problem that is unrelated.
TIA
AlpineRAM
The reason I ask is that I didn't get my hands on an 01 yet, but this could be very interesting to know before throwing MAP sensors on one that may have a problem that is unrelated.
TIA
AlpineRAM
09-21-2003, 10:52 PM
#33
Registered User
Join Date: Apr 2002
Posts: 1,135
Likes: 0
Received 0 Likes
on
0 Posts
Re:Gray smoke
Yes, with just the key on, OBD2 reports higher than atmospheric pressure. At first, I thought it was my software. Then I checked it with a normal scanner. It said the same.
I believe that all of the 01's do this. Don't quote me on that tho. I have checked one other 01 and it was the same. It was an auto as well.
I believe that all of the 01's do this. Don't quote me on that tho. I have checked one other 01 and it was the same. It was an auto as well.
09-22-2003, 12:23 AM
#34
Registered User
Re:Gray smoke
Can you switch units in your scanner software? I had some fun with a version of mine when reading metric stuff. Got it right in standard, hilarious values in metric.
AlpineRAM
AlpineRAM
09-22-2003, 02:43 AM
#36
Registered User
Re:Gray smoke
Great, Thanks!
Did you disconnect the box or just turn it off when getting the readings?
I don't know whether the sensor increases or decreases resistance with pressure, but if it increases this could point out to a contact problem that is circumvented by the ECM sensor self calibration before startup. AFAIK tha ECM takes a value for MAP before startup and uses it as a baseline for athmospheric pressure and then calculates boost from there on.
With the values you report on standstill I'd like to see what the values for boost are under load compared to readings from a mechanical gauge- are they just offset the roughly 12psi you see more at standstill or does the offset increase or decrease over real boost?
It could also be interesting whether a new MAP sensor or an APPS recalibration (mine does all sensors when going APPS recal. procedure) would change the values you see and what this would do for you performance wise.
AlpineRAM
Did you disconnect the box or just turn it off when getting the readings?
I don't know whether the sensor increases or decreases resistance with pressure, but if it increases this could point out to a contact problem that is circumvented by the ECM sensor self calibration before startup. AFAIK tha ECM takes a value for MAP before startup and uses it as a baseline for athmospheric pressure and then calculates boost from there on.
With the values you report on standstill I'd like to see what the values for boost are under load compared to readings from a mechanical gauge- are they just offset the roughly 12psi you see more at standstill or does the offset increase or decrease over real boost?
It could also be interesting whether a new MAP sensor or an APPS recalibration (mine does all sensors when going APPS recal. procedure) would change the values you see and what this would do for you performance wise.
AlpineRAM
09-22-2003, 09:38 AM
#37
Registered User
Join Date: Apr 2002
Posts: 1,135
Likes: 0
Received 0 Likes
on
0 Posts
Re:Gray smoke
I disconect the box, and there is no change.
The offset stays the same, even at full boost.
I have changed the MAP sensor, and recalibrated the APPS, with no effect.
The offset stays the same, even at full boost.
I have changed the MAP sensor, and recalibrated the APPS, with no effect.
09-22-2003, 09:53 AM
#38
Registered User
Re:Gray smoke
Well I just came back from a ride with my 98.5 and have checked MAP with OBD2- works just fine and shows me the right kPascals.
Did you send a reset all codes with the engine at standstill?
I don't know whether this is the case for your truck, but can't it be possible that the engine defuels to avoid overboost codes?
I think it would prove worthwhile to get some other 01 owners to post their results.
AlpineRAM
Did you send a reset all codes with the engine at standstill?
I don't know whether this is the case for your truck, but can't it be possible that the engine defuels to avoid overboost codes?
I think it would prove worthwhile to get some other 01 owners to post their results.
AlpineRAM
09-22-2003, 10:03 AM
#39
Registered User
Join Date: Apr 2002
Posts: 1,135
Likes: 0
Received 0 Likes
on
0 Posts
Re:Gray smoke
Reset all codes, no change.
With the fuel box removed it will set over boost codes with the turbo and injectors that I have.
I have seen a few others posting similar results, but I don't remember who they were.
With the fuel box removed it will set over boost codes with the turbo and injectors that I have.
I have seen a few others posting similar results, but I don't remember who they were.
09-22-2003, 10:28 AM
#40
Registered User
Re:Gray smoke
Well, teh overboost code with bigger injectors is OK. The ECM is only defueling to minus some fixed percentage. If boost is still going over the warning mark it will set a code.
I don't know whether your box will defuel if it senses too much boost or not. (This too much naturally higher than stock)
Hence my question about possible performance reduction.
Have you looked up whether there is a difference in the part numbers for the MAP sensor between the 99 and the 01?
AlpineRAM
I don't know whether your box will defuel if it senses too much boost or not. (This too much naturally higher than stock)
Hence my question about possible performance reduction.
Have you looked up whether there is a difference in the part numbers for the MAP sensor between the 99 and the 01?
AlpineRAM
09-22-2003, 02:49 PM
#42
Registered User
Re:Gray smoke
Well, would the MAP sensor of a 99 fit (thread and connector) ???
Could be an amusing experiment. Since we do read from the PCM and not from the ECM I think that the ECM is adapted to the higher voltage and the PCM is not so it gives wrong readings.
AlpineRAM
Could be an amusing experiment. Since we do read from the PCM and not from the ECM I think that the ECM is adapted to the higher voltage and the PCM is not so it gives wrong readings.
AlpineRAM
09-22-2003, 09:19 PM
#43
Registered User
Join Date: Apr 2002
Posts: 1,135
Likes: 0
Received 0 Likes
on
0 Posts
Re:Gray smoke
The threads would fit but it is a different plug.
I tried to fake the computer out by adjusting the voltage down until I had the correct atmospheric pressure. I never got close to that value before a code was set for MAP voltage out of range. ???
I tried to fake the computer out by adjusting the voltage down until I had the correct atmospheric pressure. I never got close to that value before a code was set for MAP voltage out of range. ???
09-22-2003, 11:58 PM
#44
Registered User
Re:Gray smoke
Well that's kind of amazing. A new DC plot to make everybody buy new MAP sensors? 
Great info on the 01 doing this. Do you know a way how to determine whether this should be like that or not, and whether a certain truck is affected or not?
AlpineRAM
Great info on the 01 doing this. Do you know a way how to determine whether this should be like that or not, and whether a certain truck is affected or not?
AlpineRAM