I am getting 4 volts from ecm

 

Is this normal? I read it is but am getting a High current code for the map sensor. I vacuum tested the sensor for a voltage drop had 4.79 Volts on my auto engunity scan tool and no drop in voltage while pulling a vacuum on the sensor while it was off the intake manifold. Bad Sensor?? I tested the signal wire from the ECM and got 4 volts while the connector was disconnected from the sensor, is that correct? or is that a bad ECM?

 

Should be 3 wire, 1 is 5v, 1 is ground, and 1 is signal. Unplugged, scan tool should read 0v i do believe.

 

Correct I have a green/white wire Ground, a green/red wire Signal, and a yellow/red 5V refrence wire, when I unplug the connector and test the connector with ignition on I am getting 4 Volt DC from the ECM on the yellow/red signal from the ECM?? That has me puzzled to get 4Volts from the ECM when that should be the signal voltage back to the ECM so the computer can adjust to the vacuum in the intake??? BAD ECM???

 

My sources say, better get a second opinion. If one is 5v, and the other is 4v, id say... ASE... Ask someone else. Sounds bad. Short to power? This site sucks too. I keep getting scareware, but ONLY on this site. Bla bla bla, your **** is infected, bla,bla,bla.click here, so we can end your life, bla,bla,bla. Lame. I'm out!

 

 

Edit... Lol...

 

Its normal. The voltage you are reading is unloaded. That is why it is always necessary to check the voltage with the connector plugged in.

Any decent mechanic with a basic understanding of how automotive electronics work can tell you that.


Based on your vacuum test above,Id say the MAP is bad.....

 

actually, testing the reference volt wire should give you almost exactly 5 volts, the only difference would be the signal wire when you plug it in, it will change at the moment you plug it in from whatever it was before you plugged it in

 

My Bad everybody, the signal wire i is green and red, not yellow and red that,s the 5V reference wire,as I posted earlier, and copied below, sorry everyone.

Earlier post!!
Correct I have a green/white wire Ground, a green/red wire Signal, and a yellow/red 5V refrence wire, when I unplug the connector and test the connector with ignition on I am getting 4 Volt DC from the ECM on the yellow/red signal from the ECM?? That has me puzzled to get 4Volts from the ECM when that should be the signal voltage back to the ECM so the computer can adjust to the vacuum in the intake??? BAD ECM???

 

Im not sure what youre asking. Let me make it easy.

If you unplug the connector and turn the ignition on,you should have:

1. Ground
2. 4.5v-5v (reference wire)
3. 1v-5v (signal return wire)


With the connector plugged into the MAP sensor:

1.Ground
2.4.7-4.9v (Refence wire,it should not read 5v plugged in)
3. Variable.(signal return) This voltage will depend on how much vaccum is present, I forget the exact specs(not more than 5v) but the info should be in your manual. The voltage should rise and fall with vaccum applied and removed.

 

DCFIVER,

You are correct, about the reaction to the map sensor, I am getting a P0108 Code over voltage/current, have returned the map sensor to autozone twice and still had the same results???? That's starting to lead me to a bad ecu/ecm??? New sensor signal voltage on scanner was 4.79, even when throttle was advanced and back to idle. Tested vacuum on intake port of the map sensor had 15 + in, vacuum at idle and vacuum guage got higher as i advanced the throttle, which led me to return the map sensor twice.??? UM???

 

What is the YMM of the vehicle?

 

It's a 2005 Honda Civic LX sedan 1.7L Automatic Trans

 

Yellow/Red is the 5v reference. It is used for ECM testing/communication. When plugged into a working sensor, it should read,4.7-4.9 volts at all times,under normal MAP function,regardless of throttle position/engine vacuum.

Green/Red is the sensor output/signal return wire. This is what you are testing for changes in output, relative to engine vacuum. With the key on, engine of(KOEO), it should read about 3-3.5v. At idle about 1v or less.


Id use a dealer MAP or equivalent,not Autozone junk.

 

I have a 2001 Honda CR-V with hesitation issues when i press the gas while in drive. I'm looking at the MAP sensor. What is the correct voltages or where can I find that info? In one place it said signal voltage should be 4.7ish with car on and engine off - I get 2.89 volts. But in another place, it was talking about a civic but they said 2.9 volts. I'm inclined to believe that because I replaced the sensor with a used one and also got 2.89 volts, then I bought a new one and got 2.89 volts. I cut the wire near the PCM to check for shorts, but it checks out fine. In this thread I see someone say that the input voltage shouldn't be more than 5, but mine is 5.05. I didn't see that as a problem, but maybe that is a problem? The ground seems fine too. I'm very confused.

 

Why do you think your hesitation issues are MAP related ?

 

All I'm getting for trouble codes is random misfire, so either timing is off or fuel/air ratio is off. I had a rough idle a year ago and ended up replacing a bunch of parts including Idle air control valve, distributor cap, rotor, ignition coil, a fan, the switch for the fan, and i also did a valve adjustment. This time the issue doesn't feel quite the same as last year when I had all around rough idle and poor performance (it ended up being the IAC). I reset the TPS last year too and tested it's voltages this year and it tests fine. Fuel filter seems fine, and when i took it out there was enough back pressure that makes me think the fuel pump is fine too. I wouldn't think it was a spark plug or fuel injector because i don't get a misfire for a specific cylinder. Also, when i turn it on it starts just fine. I can rev the engine in park and it sounds fine. I put it in drive and it idles fine, until I press the gas - then it hesitates immediately and afterwards idle is a little weird too. When driving it there is a continued hesitation when pressing accelerator and loss of power going up hills. It gets up to speed, but fuel efficiency is obviously down and it just feels like it's going to do some long term damage unless i figure out whats wrong with it. It also started doing this kind of suddenly. I drove to town and it was fine, but on the way back was acting up. Upon return i popped the hood and it was pretty hot. After it cooled i saw the coolant was a bit low,so i topped it off, drove it, topped it off, etc and now it maintains the coolant level (finally got all the bubbles out), but the hesitation/ poor performance persists. Any ideas?

 

After you have tested the ignition and fuel systems you should perform compression and leak down tests on the engine.

I used to have a link to the actual Honda diagnostic trouble shooting procedures for random misfire but I lost it. This one is close - at least it is a guideline to follow rather than a hit and miss random part replacement strategy.

https://www.fixdapp.com/blog/p0300-honda