"MAP" Sensor tests and data. 1.6L 8v only
MAP = Manifold Air Pressure , sensor, or "Baro"
How to connect and test the map sensor on the firewall, not removed is here.
Data is in the Yellow fields.
The 1995 FSM shows a graph that is only altitude correction and not MAP /pressure of a running engine.
My data is from a 91-95' Suzuki Sidekick. 8 valve engine, this sensor controls all fueling , the ECU uses it to calculate are flow , through the engine to match up correct fueling.
( this sensor below is NOT the EGR MAP MDP)
All voltages below must be corrected for altitude differences. see link below for those rules.
A general rule, is to subtact 0.1 volts for every 1000 feet above sea level.
The below is at sea level.
The sensor is also called a baro sensor, (short for barometer)
The Map sensor is absolute, such that it measures, maximum voltage, keyon or removed and connected to free air space (free atmosphere) the opposite of the mechanics gauge (relative).
Chart #1 the top row is your mechinics tool connected to the plenum chamber (intake manifold) I am using a vacuum hand pump below, for the yellow data.
HG, is USA units for column of mercury in inches. Bar and kPa gauges are mostly used outside of the USA.
The sensors output, is linear and has no drop outs, if you see odd readings it is a bad MAP sensor.
The above reading are a very strong engine , lower cylinder compression, can have lower idle vacuum.
If there is no 5vdc on the map power pin, the MAP will be dead. (same with ground pin) the 5vdc is MAP power supply.
The Map output is analog linear. See graphics below, there must not be drop outs are glitches to 5v or the MAP is bad. (wiring good)
How to test the MAP on car?:
Key on, no start , the Map should go to 3.9 vdc at sea level (less at high altitude see link far below...) "make sure this voltage makes it to the ECU"
Attach a hand vacuum tool to the MAP nipple and pump it down to 23 inches HG the voltage out of the MAP will be about 0.8v.
Put the MAP vacuum hose back on to the MAP, from Throttle body.
Start the engine, the map will read about 1.5vdc. (sea level)
Gun the motor to wide open throttle , for an instant and the MAP, will read 3v for an instant at W.O.T the release the throttle and see 0.5v or near.
Do not test the MAP with a motor, that has low oil. (or the oil lamp is stuck on)
The MAP sensor can be fooled.: by: (DTC code 31/32 )
Most new MAP sensor intalled do nothing at all, and make the sensors makers very rich.
The Vacuum hose route, on USA cars are fully documented, on the vacuum map graphic, found under the hood. Or look here.
WOT = Wide open Throttle ( you never quite get to 0 Hg. , except key on not started you do)
Normal Idle is 800 RPM
Decel= Deceleration, is flying down a hill in 2nd gear, foot off accelerator , max vacuum generated then , over 25 inches HG. using engine braking !
Jargon words are here.
You never quite get to perfect vacuum and of course, is effected by Altitude ( I am at sea level + 500 ft. for yellow data)
? = I couldn't pump that high. My FSM shows 0.3v at 28" Hg , I get 0.27vdc mine.
If KPa is you system use the conversion tables to get you answers.
KPa= 1000 x Pa or 1000 x (N/m2)
If you have a vary RARE OBD1 scan tool?
Your scan tool may read in Volts or in BAR , mm-HG, KPa or inches of Mercury "HG" Varies by country who made the tool.
Suzuki altitude compensation rules.
For fun, see Ford MAP, this works the same.
The left side is pressure and not a vacuum gage reading, so read it backwards for relative pressure.
Key on volts is at max pressure , this is the total weight of the atmostphere (absolute) like a weather barometer.
The ECU actually uses pressure, to calculate air flow through the engine. (and air temperature)
Key on is 4.5v, idle is near middle and max vacuum load deceleration, is 0.5v (or near)
If you don't have an absolute Bar meter, the graph below is useless.
The graph below, is what the ECU uses in it's internal calculations.
My Jeep chart is below , (HG plot , USA) All these MAP sensors, work like this.
Manifold Air Pressure (abs.)
This chart is off a real sensor, on a Jeep.
Graphic #2: (I offer this to my Jeep friends, that don't have this graphic x/y plot, and is missing in my 2008 FSM)
The vacuum on the bottom axis , is a real mechanics vacuum gage, inches HG. (relative) Just like your shop tool has.
The left side is keyon, not started. about 4 volts d.c. or tad more. Any voltmeter connected to the output pin will show this reading.
The right side is easy deceleration, foot off the throttle, pulling say, 23"HG hard vacuum (from a faster speed, it can hit 27inches, easy, and get near 0 volts)
At idle the voltage is at 20" HG. (1.25v?)
Racing the engine fast, say in Neutral, you will see 10" HG. and 3vdc
The correct pin numbers changed over the many years. (check your FSM carefully)
Old Jeeps pin B (center) is output pin, on year 2000 the center pin 2 is MAP output, DG-RD(darkgreen-red)
on newer Jeeps , 2007 and newer there are 3 pins, called 1,2,3, not A,B,C.
Pin1 is violet-brown output pin.
Pin 2 is ground, DB-DG (dark blue and dark green) 0 volts DC all the time.
Pin 3 is +5vdc power input, to sensor. and is YL/PK (yellow pink) the 5volt line runs 7 sensors on my care, it don't fail with out, huge DTC dumps. This is PCM power out.
It should go with out saying, if a mechanics vacuum hand tool , shows the same bad vacuum, as the MAP output, then the engine is bad. (or horrid vacuum leaks)
or if the live OBD2 MAP plots bounce,like mad, and the mech. hand tool does, too, then the engine is bad. Most MAPs don't fail, use a hand tool to prove that easy.
The vacuum at , near 20 inches, and STEADY.
The ECU will go quite nuts, with a bouncing MAP signal.
The ECU can not run a bad engine, heck , nothing can.
Ground reads 0v
5v pin reads hear 5v
and the output varies directly as vacuum does, just like the chart above.
A general rule, is to subtact 0.1 volts for every 1000 feet, above sea level. This fact, corrects fueling for altitude changes.
Use a back-probing needle lead to test the output pin.
In a pinch, go to walfart, and the sewing department and buy the $1 leather needle kit, then connect it to your aligator test leads. or solder it to your probe tip.
Ebay: New Hantek Back Pinning Probes
Facts: ( there are many standards for pressure or vacuum)
The Latin word hydrargyrum (means liquid silver,or Mercury) is the real meaning of HG. and in the USA it's in inches , in other countries it's mmHG or BAR. (mm is millimeter)
29.53" HG = 1 bar = 100kPA (kilo Pascal's) = 749 mm HG = 14.503 PSI = 0.987 athmosphere's.
On cars, we don't use a mercury columns any more (toxic metal), we use a presssure transducer, that is called a MAP or baro sensor.
On modern cars, we use the OBD2 scan tool and check the data from the MAP. (with mechanics, vacuum gauge attached
to the intake plenum. (any nipple below the throttle valve)
I check 3 or 4 data points: keyon, idle, racing at 3000 RPM ,then at 3k , I cut the throttle to see how high a vacuum, I can get.
( keyon=0-hg, Idle=19hg, 3k-RPM=10 hg, and deceleration= 25 hg)
On OBD1 car , we use a voltmeter , back probed to the MAP output pin and do the 4 data points. (takes me what, 10 minutes?)
Someone asked what is a data point?, Answer, it's 3 voltage points on the graph above.
Rev.: 10 7-6-11 ( added charts, 4-14-2014, fixe bad link to)