slow96lude

Ok gurus here you go. I went to check out the map and tps sensors because I have a code for the map sensor. When I initially checked the voltage to the sensors (both of them from the ecu) it was 5v. Then All of a sudden it went to full 12 volts. And both outputs were at 9v. What could have caused this. Another thing before it went to 12v, there was no output voltage from either sensor...Whats the deal? I also have a code for the 02 sensor. FYI

Former User

Where exactly are you making the voltage measurements?

Are you using a digital multimeter to measure voltage?

Are measurements made with the key in ON(II)?

Bwill9886

Ok, 2 questions before moving on:

1) Are you sure the voltmeter was correctly set/working correctly? Not trying to offend you but I know I've screwed up the wires or had it set to the wrong function a few times. If we eliminate the voltmeter as a suspect, then we can move on to...

2) Defining "all of the sudden". No need to write an essay, but if we can find out what happened in between your last reading and the most recent, it might tell us something. If there is no output voltage, then they aren't receiving power. Have you tested the wires leading up to the sensors?

Answer these and hopefully we can better troubleshoot. I just recently went through a wiring mess in my friends Civic to fix BOTH of these sensors so their wiring is still fresh in my memory... fortunately or unfortunately haha

slow96lude

OK so im not new to using a multimeter for one...lol I had it set to 10v and I now it was working properly because it measure 5v before the all of a sudden happened. I was measuring the 5 volts for the yellow and white wire on the tps. And yes the car was in the on pos not running. And I also did it when the car was runnin.

slow96lude

The wiring is pretty hacked up. I just got the car today. It is a 95 hatch with a hackjob of a ls swap done to it. Im pretty sure they have the right sensors plugged into the right plug.

Former User

Digital or analog multimeter?

From the Honda Civic service manual:

Bwill9886

Gotta love hackjob wiring... never fails to cause major headaches and a lot of wasted hours in the garage. You are testing the same wires too right? I know its dumb but I've done it before when I was tired haha.

So it just one day read differently huh? Well that is strange, and thats why I asked about your use of the voltmeter. Didn't know if maybe you just happened to change something on it and all the sudden it changed the voltage reading.

Can you let us know whether its digital or analog?

Also answering whether you've tested the power wiring at the sensor would help as well.

slow96lude

its analog. but it a really nice one. So I just went out and tested again, and this time i got better results. The signal on tps was almost 0v at closed throttle and 4v wot. I adjusted acordingly and the throttle response picked up. Now about the map. This time the signal was at 3.5v no vac. And i started the car and it went to about .5v. I think i need a new map sensor because it will not go to the 5v or w/e it is supposed to have with no vac. I wont go above 3.5v is what im tryin to say..I know that since im using a analog meter the reading could be off slightly but i wouldnt say 1.5v off

Former User

The larger risk is that use of an analog multimeter will damage the ECU.

slow96lude

how exactly does that happen.

Bwill9886

Honestly just google it. I was wondering why your readings seemed wierd...

Get yourself a good digital (like 20 bucks at Home Depot or Lowes) and go and test again. Then you can move forward.

slow96lude

alright will do. I should have probably gotten one a long time ago because i work on so many cars. But do you guys think the map sensor is bad? only putting out 3.5v.

Former User

An analog multimeter permits a relatively large amount of electrical current to flow through the tested circuit during voltage measurements. This high current flow has the potential to damage sensitive circuits, such as those in the ECU. In contrast, a high impedance digital multimeter permits only a small amount of current flow during voltage measurements. Therefore, unless otherwise specified, use a high impedance digital multimeter for troubleshooting all of your car circuits.

Former User

I think the MAP sensor may be fine (see below). What CEL code do you have?

slow96lude

got code 3. also 41. Which is weird because even after resetting the ecu and the car is cold it shoots me a 41. I didnt think that the ecu even read the o2 sensor untill it was warmed up