Obd1 sensor problems
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Mountain Pass
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Obd1 sensor problems
Hi all
I have a 1986 ford f150 and I did a obd1 scan on it. I scanned it with the key on and the engine off and it said my map sensor was bad. When I did a test with the engine on it said my o2 sensor was bad. Which one is which? I am trying to test the map sensor but how do I tell which plug is the 5 volt supply and which one is the signal?
I have a 1986 ford f150 and I did a obd1 scan on it. I scanned it with the key on and the engine off and it said my map sensor was bad. When I did a test with the engine on it said my o2 sensor was bad. Which one is which? I am trying to test the map sensor but how do I tell which plug is the 5 volt supply and which one is the signal?
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From: Virginia
Key on, Engine off (Ford calls it KOEO) looks around at the sensors in their steady state. The key on engine running test (KOER) reads the sensors with the engine active. If you do not wait till the engine is completely warmed up, you will get codes. The engine has to run awhile and the O2 sensor has to heat up before it will work. Before the O2 heats up this is called "open loop" running of the engine. When the O2 sensor warms up and starts sending a signal to the computer, this puts the computer into "closed loop".
Your O2 code could be simply the sensor was not heated up.
The guy in the book says the MAP sensor generates a frequency square wave. The frequency varies depending on the atmospheric pressure. He says when the key is first turned on but the engine hasn't been started yet, it quickly samples the MAP sensor and uses this as a baseline for all other readings. He says depending on your altitude, this initial square wave frequency is 160hz. He says you can use a frequency counter to test the MAP, or a tachometer. He says a frequency of about 160hz will generate a reading of about 4800rpm. He says at idle the frequency should be about 110hz to 120hz.
When looking at the sensor, the vacuum port is on the far left. The wire next to the vacuum port is the 5 volt wire. The center wire will have the frequency output on it, and the wire on the far right farthest from the vacuum port is the sensor ground. He said you leave it all plugged in, and tap into the wires while they are still plugged in to run the tests.
If you are wondering where I am getting all this info, it's out of this book. Sounds like you are getting into this system, this book is worth every penny you pay for it.
Your O2 code could be simply the sensor was not heated up.
The guy in the book says the MAP sensor generates a frequency square wave. The frequency varies depending on the atmospheric pressure. He says when the key is first turned on but the engine hasn't been started yet, it quickly samples the MAP sensor and uses this as a baseline for all other readings. He says depending on your altitude, this initial square wave frequency is 160hz. He says you can use a frequency counter to test the MAP, or a tachometer. He says a frequency of about 160hz will generate a reading of about 4800rpm. He says at idle the frequency should be about 110hz to 120hz.
When looking at the sensor, the vacuum port is on the far left. The wire next to the vacuum port is the 5 volt wire. The center wire will have the frequency output on it, and the wire on the far right farthest from the vacuum port is the sensor ground. He said you leave it all plugged in, and tap into the wires while they are still plugged in to run the tests.
If you are wondering where I am getting all this info, it's out of this book. Sounds like you are getting into this system, this book is worth every penny you pay for it.
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Mountain Pass
Joined: Feb 2021
Posts: 180
Likes: 10
Key on, Engine off (Ford calls it KOEO) looks around at the sensors in their steady state. The key on engine running test (KOER) reads the sensors with the engine active. If you do not wait till the engine is completely warmed up, you will get codes. The engine has to run awhile and the O2 sensor has to heat up before it will work. Before the O2 heats up this is called "open loop" running of the engine. When the O2 sensor warms up and starts sending a signal to the computer, this puts the computer into "closed loop".
Your O2 code could be simply the sensor was not heated up.
The guy in the book says the MAP sensor generates a frequency square wave. The frequency varies depending on the atmospheric pressure. He says when the key is first turned on but the engine hasn't been started yet, it quickly samples the MAP sensor and uses this as a baseline for all other readings. He says depending on your altitude, this initial square wave frequency is 160hz. He says you can use a frequency counter to test the MAP, or a tachometer. He says a frequency of about 160hz will generate a reading of about 4800rpm. He says at idle the frequency should be about 110hz to 120hz.
When looking at the sensor, the vacuum port is on the far left. The wire next to the vacuum port is the 5 volt wire. The center wire will have the frequency output on it, and the wire on the far right farthest from the vacuum port is the sensor ground. He said you leave it all plugged in, and tap into the wires while they are still plugged in to run the tests.
If you are wondering where I am getting all this info, it's out of this book. Sounds like you are getting into this system, this book is worth every penny you pay for it.
https://www.amazon.com/Tune-Modify-F.../dp/0879386215
Your O2 code could be simply the sensor was not heated up.
The guy in the book says the MAP sensor generates a frequency square wave. The frequency varies depending on the atmospheric pressure. He says when the key is first turned on but the engine hasn't been started yet, it quickly samples the MAP sensor and uses this as a baseline for all other readings. He says depending on your altitude, this initial square wave frequency is 160hz. He says you can use a frequency counter to test the MAP, or a tachometer. He says a frequency of about 160hz will generate a reading of about 4800rpm. He says at idle the frequency should be about 110hz to 120hz.
When looking at the sensor, the vacuum port is on the far left. The wire next to the vacuum port is the 5 volt wire. The center wire will have the frequency output on it, and the wire on the far right farthest from the vacuum port is the sensor ground. He said you leave it all plugged in, and tap into the wires while they are still plugged in to run the tests.
If you are wondering where I am getting all this info, it's out of this book. Sounds like you are getting into this system, this book is worth every penny you pay for it.
https://www.amazon.com/Tune-Modify-F.../dp/0879386215
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Joined: Jan 2001
Posts: 56,992
Likes: 2,741
From: Virginia
Well, you could then have a bad O2 sensor also. They do wear out. I have heard people having a lot of problems buying cheap sensors also, though replacement parts of all types seem to have a lot of problems lately. The guy in the book says you can put a digital voltmeter on the O2 sensor leads (not the heater lead) and when the engine is warmed up, you should see the voltage swing back and forth, going above .45 volts, then going below .45 volts. The computer richens the mixture, and then leans the mixture constantly, and this averages out the fuel ratio voltage from the O2 sensor at .45 volts. If the voltage stays less than .45 volts, the computer interprets this as a lean condition. Above .45 volt is a rich condition. You have to decide by troubleshooting if the O2 sensor is telling the truth and you have a engine problem, or is it lying and it is a bad O2 sensor.
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Krisverde
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