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map sensor

posted Jun 06, 2016 17:37:57 by CyrusKiur
Hey guys?I nid help here.I would like to know how 1 bar map sensor works.have been repairing Toyota vigo turbocharger problems by replacing map/baro sensor.am used to see map/baro changing pressure as i press the gas from 65 to 180 pdi but 1 bar map doesnt change at all.if anybody has the knowledge of this kindly share it with me.
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9 replies
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IvanKibuka-Kiguli said Jun 06, 2016 18:13:23
If it is a 3-wire sensor, I believe the PID value range may look different between cars and even models but should change up as boost is being generated by the turbo, regardless of the units used. It should also read local atmospheric pressure KOEO. If I didn't register change on the scantool, I would back probe the sensor signal wire and look for voltage changes as boost is being created. If no voltage change is seen, I would confirm 5V reference and ground first before looking for a short to ground or open on the signal wire. If all that passed, I would then bypass test it with a test light to B+ to confirm signal wire integrity. If that passed, then I think I would either be looking at a bad sensor or a turbo that is creating nil boost or serious air charge leak(s). If all failed, I would be really stumped and would come here to ask the guys.
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CyrusKiur said Jun 06, 2016 19:03:33
Oh good and thank for the help.so the scan tool Pid should change.the scan tool Pid don't change at all.map remains 1 bar no matter how I press the gas.turbocharger boost is ok,have changed the turbo already.have not check the 5 volt reference,ground and signal wire but i just assume are ok because no check engine light.I thought 1 bar map dont change?right?
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CyrusKiur said Jun 07, 2016 19:14:48
Confirmed!the sensor is ok,no air leakage,turbocharger is working fine,sensor signal wire integrity is fine but the map sensor signal voltage changes from 0.87 to 1.3 no matter how I press the gas.I nid help here guys.
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IvanKibuka-Kiguli said Jun 08, 2016 04:04:32
Did you press the gas while the transmission was in neutral or in actual driving/loaded conditions? If the former, the signal voltage probably won't read higher than 1.3V because the turbo will only charge so much in neutral transmission conditions, regardless how fast you run the engine. The ECM will probably cut fuel beyond a certain RPM. What are the actual driveability symptoms with this truck?
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CyrusKiur said Jun 08, 2016 08:55:48
Neutral condition.the car doest have power wen on hills.
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IvanKibuka-Kiguli said Jun 08, 2016 09:17:14
If it were me, I would test the MAP/boost pressure sensor signal voltage with the car under load. If the sensor passes but reading doesn't change on scantool, I would think about either an open/short in the signal wire or bad ECM. If all those checked out, the problem could be elsewhere, not the turbo. I would investigate exhaust pipe restriction and injectors next.
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CyrusKiur said Jun 08, 2016 09:21:19
he signal voltage probably won't read higher than 1.3V because the turbo will only charge so much in neutral transmission conditions, regardless how fast you run the engine. The ECM will probably cut fuel beyond a certain RPM. (Do u mean turbo charges more in neutral condition or in load condition?
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IvanKibuka-Kiguli said Jun 08, 2016 10:30:26
All turbos charge more at higher RPMs because the turbine spins faster. I am assuming this one is a VNT/VGT type. To my knowledge, the ECM controls the position of vanes on the exhaust pipe side of the turbine which interferes with the angle at which the exhaust gases impinge on the turbine blades. If the ECM doesn't want the turbo to charge any further because it doesn't see load, it will actuate a vacuum solenoid/valve to place the vanes in such a position that the turbo can't charge any further. If the engine is loaded, it will place the vanes in a position where the turbo generates the optimum charging for the load and accelerator pedal position (which should generally be more than is achievable when the engine is not loaded). In short, the turbo charges more under load.
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CyrusKiur said Jun 08, 2016 16:02:13
Thank for help.
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