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GM 3 bar install... getting random check engine light, no codes

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GM 3 bar install... getting random check engine light, no codes

Old 09-28-2008, 11:36 PM
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Default GM 3 bar install... getting random check engine light, no codes

threw a GM 3 bar on today... during tuning i was getting a check engine light (never before the 3 bar)

it would light up and go away if i go into neutral and give it some gas

no ECU codes.

the car runs fine when the light comes on.. its weird.

ECU is a PM6 OBD0 running turbo edit (setup for a 3 bar)

the check engine light seems to come on when its at low throttle like going down a hill... or when slowing to go over bumps...

anyone have any ideas? i was thinking cold solder joint but wouldnt that give me a map sensor ECU code? (the solder joints all look fine)





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Old 09-29-2008, 12:24 AM
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Default Re: GM 3 bar install... getting random check engine light, no codes

to sum it up, you fail at life.


any more questions?


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Old 09-29-2008, 02:43 AM
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Default Re: GM 3 bar install... getting random check engine light, no codes

what was the problem?
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Old 09-29-2008, 12:33 PM
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Default Re: GM 3 bar install... getting random check engine light, no codes

early doses of fail mixed with chances of aids in the later hours?? thats my guess.


hopfully someone who isnt a retard will chime in and let us know. haha


it did it to me again heading into the timmy ho's parking lot.. quick blip of throttle in neutral and light is gone...

no flashing lights on the ECU or codes to read...
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Old 09-30-2008, 10:27 AM
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Default Re: GM 3 bar install... getting random check engine light, no codes

have you been datalogging to see if there is anything weird happening when your CEL comes on?

i would bet that its something to do with the voltage the ecu sees...because the larger the map sensor, the less of the 0-5v range is in vacuum. so if you see a large amount of vacuum on decel, it might be below the minimum voltage of the sensor.

also, did you map sensor come with a datasheet (showing voltage and absolute pressure relationships)? is so, send it to me please...i will check the formulas in TE...

do you have the o2 off with a wideband hooked up to the nb02 input? because that used to give me random cels when engine braking... i doubt thats it, but just thought id ask anyways.
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Old 09-30-2008, 01:43 PM
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Default Re: GM 3 bar install... getting random check engine light, no codes

the wideband goes through the stock o2 sensor wire. scaled to 3.5v max. (been running like this for MONTHS without any issues/lights... although since the tune changed the values from the o2 sensor would have changed as well)

no datasheet came with the GM 3 bar, but ill look.

i havnt been datalogging but i have been watching the map trace when the light comes on, and its not doing anything weird. but ill try some datalogging to see if that is more detailed.
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Old 09-30-2008, 01:46 PM
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Default Re: GM 3 bar install... getting random check engine light, no codes

found this... hope it helps.

"For GM Map sensor, go to options -> full list -> MAP kPa C =0, MAP Kpa m=300, MAP max = 4.98V, MAP min = .35V"


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Old 09-30-2008, 02:06 PM
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Default Re: GM 3 bar install... getting random check engine light, no codes

Originally Posted by danz
the wideband goes through the stock o2 sensor wire. scaled to 3.5v max. (been running like this for MONTHS without any issues/lights... although since the tune changed the values from the o2 sensor would have changed as well)

no datasheet came with the GM 3 bar, but ill look.

i havnt been datalogging but i have been watching the map trace when the light comes on, and its not doing anything weird. but ill try some datalogging to see if that is more detailed.
see if you can tell what teh map sensor voltage is and what the map value is when the cel comes on...using ecucontrol... (without killing anyone!)

do you have a boost/vacuum gauge? if so are the map values in ecucontrol close with the 3-bar?

what kind of vacuum readings are you getting when the cel comes on? is it greater than 25 inHg (i.e. 27 inHg, or 30 inHg)?
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Old 09-30-2008, 02:41 PM
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Default Re: GM 3 bar install... getting random check engine light, no codes

the manual vac gauge shows that the GM 3 bar is working fine. car drives well. the map trace is sharp and concise.

the vacuum readings when the light comes on vary, but its usually around -20inHg (guess). usually at a very light cruise, to the point id be slowing down without wheel breaking but the foot is still on the gas, JUST...

its hard to know the exact manifold pressure as im usually looking at the road not the laptop... but i tried to bring up the RPMS to create a good vacuum and closing the TB but that doesnt make the light come on... its only when crusing. its weird.

ill do some datalogging after work and see if i can get specifics. a very good idea.

i havnt been able to reproduce the engine light... it just happens when it happens. im gonna recheck my solder joints after work too.

the output of the GM 3 bar is linear
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Old 09-30-2008, 03:50 PM
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Default Re: GM 3 bar install... getting random check engine light, no codes



Info for GM Part # 12223861

PRESSURE RANGE, OPERATING
40-304 kPa

MAX.
700 kPa

ACCURACY
1% to 5%

OPERATING TEMPERATURE
-40 to +125 C

SUPPLY VOLTAGE
5.1+/- 0.36V dc

SUPPLY CURRENT
<10 mA V dc

here is a chrome offset and scaler settings... not sure if these apply to TE at all.

GM 3-bar part # 12223861
Scaler 628
Offset 0

for additional information:

Tuner also said the Neetronics 3bar would probably be close to the GM 3bar. The setting for that one are as follows:
Scalar: 625 mbar/volt
Offset: 42 mbar

The Motec 3bar settings are as follows:

Scalar09 mbar/volt
Offset: 2 mbar

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