gmrulz4u Posted June 25, 2003 Report Posted June 25, 2003 I was curious as to how my MAP Sensor was functioning, because it tends to read a little on the high side, so tonight I did the following: I took my tried, tested & true Digital MultiMeter out to the car along with a set of short needle-nose pliers, I started the car, hooked up the MultiMeter to read the MAP Sensor's voltage, it was at about 1.72 volts. I then grabbed the pliers and squuuuuuueeezed the MAP Sensor vacuum hose ALL the way so that it would be completely blocked-off, and assumingly would not be able to measure any vacuum... And now for the part that makes NO sense to me: The MAP Sensor voltage did NOT change AT ALL!!!!??? What the hell!? I thought it would go to at LEAST 3 or 4 volts + Can someone with any knowledge please tell me what the heck I'm missing here? This can't be right... THANKS! Quote
Slade901 Posted June 25, 2003 Report Posted June 25, 2003 Well, check the voltage on the Map sensor with the Ignition in ON position and note the reading. Start the car and let the engine run at IDLE. The voltage should drop. Rev the Engine and the voltage should gradually increase. Quote
Robby1870 Posted June 25, 2003 Report Posted June 25, 2003 If the MAP reads no vacuum, the ECM will go to a safe mode, or thats what I call it. Like, I had the vacuum line pinched and didnt know, started the car, ran rough for a little bit, then when the SES light came on, it idled fine. Now, it wouldnt drive right, but it was good enough to drive it a little. Thats why I call it safe mode, like the ECM goes to a second default fuel table and uses that so that you can get home if your out on the road. So, yours might be doing that. Just a suggestion Robby Quote
paulo57509 Posted June 25, 2003 Report Posted June 25, 2003 I was curious as to how my MAP Sensor was functioning, because it tends to read a little on the high side, so tonight I did the following: I took my tried, tested & true Digital MultiMeter out to the car along with a set of short needle-nose pliers, I started the car, hooked up the MultiMeter to read the MAP Sensor's voltage, it was at about 1.72 volts. I then grabbed the pliers and squuuuuuueeezed the MAP Sensor vacuum hose ALL the way so that it would be completely blocked-off, and assumingly would not be able to measure any vacuum... And now for the part that makes NO sense to me: The MAP Sensor voltage did NOT change AT ALL!!!!??? What the hell!? I thought it would go to at LEAST 3 or 4 volts + Can someone with any knowledge please tell me what the heck I'm missing here? This can't be right... THANKS! What you're seeing is normal. Take a minute to think about what you just did. Consider just the vacuum line and the MAP sensor. Unless there is a vacuum leak, just pinching the line isn't going to do anything. There is still the same vacuum between the pliers and the sensor. Hook up your DVM to the sensor and just remove the vacuum line. Now (if all is well) you should see a voltage change on the DVM. Quote
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