MAP sensor
Seasoned HDF Member
Joined: Aug 2008
Posts: 5,034
Likes: 981
mr. im makes a valid point
in electronics, the rule of order is check power supply. things go wonky when power is not right. most sensors today use a lower source, aka 5 volt, since tech has gone wayyyy past transistor logic which typically was 12 volts. higher voltage is used in power where as lower in for control, wayyyy easier to trouble shoot. the same goes for ground source since it is easier to find a positive potential than a negative since most are referenced to engine ground. HOWEVER, that does not mean everything is ground sourced since you can have a so called ground source with two positive potentials.
one of the biggest concerns is in how clean the power supply is. in the analog, hash was tolerated but not so digital because because hash can mess up the logic and computers are stupid, can only do as commanded. that said, i would check for excessive AC ripple. you will always have some but the battery is like a giant capacitor and will absorb it.
case in point: when digital came out, chrysler has serious issues as the vehicle got older, why??? well, the alternator still used segmented armature and as it wore, the output was spiked and that introduce hash which overwhelmed the system and made diagnostics hard until they found out the issue, so now the alternator has slip rings.
bad grounds and iffy connection are a common issues. today, data logging is most important but most do not have the $$$$$ equipment so shops make $$$$$.
in electronics, the rule of order is check power supply. things go wonky when power is not right. most sensors today use a lower source, aka 5 volt, since tech has gone wayyyy past transistor logic which typically was 12 volts. higher voltage is used in power where as lower in for control, wayyyy easier to trouble shoot. the same goes for ground source since it is easier to find a positive potential than a negative since most are referenced to engine ground. HOWEVER, that does not mean everything is ground sourced since you can have a so called ground source with two positive potentials.
one of the biggest concerns is in how clean the power supply is. in the analog, hash was tolerated but not so digital because because hash can mess up the logic and computers are stupid, can only do as commanded. that said, i would check for excessive AC ripple. you will always have some but the battery is like a giant capacitor and will absorb it.
case in point: when digital came out, chrysler has serious issues as the vehicle got older, why??? well, the alternator still used segmented armature and as it wore, the output was spiked and that introduce hash which overwhelmed the system and made diagnostics hard until they found out the issue, so now the alternator has slip rings.
bad grounds and iffy connection are a common issues. today, data logging is most important but most do not have the $$$$$ equipment so shops make $$$$$.
Thread Starter
|
Cruiser
Joined: Aug 2012
Posts: 128
Likes: 22
From: West Michigan
Good as far as I can tell. Voltmeter shows proper function while running, no idiot lights, no codes thrown other than "MAP sensor failure"
Thread Starter
|
Cruiser
Joined: Aug 2012
Posts: 128
Likes: 22
From: West Michigan
mr. im makes a valid point
in electronics, the rule of order is check power supply. things go wonky when power is not right. most sensors today use a lower source, aka 5 volt, since tech has gone wayyyy past transistor logic which typically was 12 volts. higher voltage is used in power where as lower in for control, wayyyy easier to trouble shoot. the same goes for ground source since it is easier to find a positive potential than a negative since most are referenced to engine ground. HOWEVER, that does not mean everything is ground sourced since you can have a so called ground source with two positive potentials.
one of the biggest concerns is in how clean the power supply is. in the analog, hash was tolerated but not so digital because because hash can mess up the logic and computers are stupid, can only do as commanded. that said, i would check for excessive AC ripple. you will always have some but the battery is like a giant capacitor and will absorb it.
case in point: when digital came out, chrysler has serious issues as the vehicle got older, why??? well, the alternator still used segmented armature and as it wore, the output was spiked and that introduce hash which overwhelmed the system and made diagnostics hard until they found out the issue, so now the alternator has slip rings.
bad grounds and iffy connection are a common issues. today, data logging is most important but most do not have the $$$$$ equipment so shops make $$$$$.
in electronics, the rule of order is check power supply. things go wonky when power is not right. most sensors today use a lower source, aka 5 volt, since tech has gone wayyyy past transistor logic which typically was 12 volts. higher voltage is used in power where as lower in for control, wayyyy easier to trouble shoot. the same goes for ground source since it is easier to find a positive potential than a negative since most are referenced to engine ground. HOWEVER, that does not mean everything is ground sourced since you can have a so called ground source with two positive potentials.
one of the biggest concerns is in how clean the power supply is. in the analog, hash was tolerated but not so digital because because hash can mess up the logic and computers are stupid, can only do as commanded. that said, i would check for excessive AC ripple. you will always have some but the battery is like a giant capacitor and will absorb it.
case in point: when digital came out, chrysler has serious issues as the vehicle got older, why??? well, the alternator still used segmented armature and as it wore, the output was spiked and that introduce hash which overwhelmed the system and made diagnostics hard until they found out the issue, so now the alternator has slip rings.
bad grounds and iffy connection are a common issues. today, data logging is most important but most do not have the $$$$$ equipment so shops make $$$$$.
I do like to learn though.
Seasoned HDF Member
Joined: Feb 2007
Posts: 6,034
Likes: 1,099
From:
Use a digital voltage meter at battery terminals to review DC voltage.
Do not use a dash meter.
With the bike parked..
Check voltage before starting with everything OFF and write down voltages.
Then write down voltages for:
While cranking.
At low idle
At a steady high RPM.
When you have checked the above then go back and check if AC voltage is slipping to battery.....yes AC voltage while the bike is at low idle and then a steady HIGH RPM.
Do not use a dash meter.
With the bike parked..
Check voltage before starting with everything OFF and write down voltages.
Then write down voltages for:
While cranking.
At low idle
At a steady high RPM.
When you have checked the above then go back and check if AC voltage is slipping to battery.....yes AC voltage while the bike is at low idle and then a steady HIGH RPM.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,703
Likes: 7,887
From: poway
mr. im makes a valid point
in electronics, the rule of order is check power supply. things go wonky when power is not right. most sensors today use a lower source, aka 5 volt, since tech has gone wayyyy past transistor logic which typically was 12 volts. higher voltage is used in power where as lower in for control, wayyyy easier to trouble shoot. the same goes for ground source since it is easier to find a positive potential than a negative since most are referenced to engine ground. HOWEVER, that does not mean everything is ground sourced since you can have a so called ground source with two positive potentials.
one of the biggest concerns is in how clean the power supply is. in the analog, hash was tolerated but not so digital because because hash can mess up the logic and computers are stupid, can only do as commanded. that said, i would check for excessive AC ripple. you will always have some but the battery is like a giant capacitor and will absorb it.
case in point: when digital came out, chrysler has serious issues as the vehicle got older, why??? well, the alternator still used segmented armature and as it wore, the output was spiked and that introduce hash which overwhelmed the system and made diagnostics hard until they found out the issue, so now the alternator has slip rings.
bad grounds and iffy connection are a common issues. today, data logging is most important but most do not have the $$$$$ equipment so shops make $$$$$.
in electronics, the rule of order is check power supply. things go wonky when power is not right. most sensors today use a lower source, aka 5 volt, since tech has gone wayyyy past transistor logic which typically was 12 volts. higher voltage is used in power where as lower in for control, wayyyy easier to trouble shoot. the same goes for ground source since it is easier to find a positive potential than a negative since most are referenced to engine ground. HOWEVER, that does not mean everything is ground sourced since you can have a so called ground source with two positive potentials.
one of the biggest concerns is in how clean the power supply is. in the analog, hash was tolerated but not so digital because because hash can mess up the logic and computers are stupid, can only do as commanded. that said, i would check for excessive AC ripple. you will always have some but the battery is like a giant capacitor and will absorb it.
case in point: when digital came out, chrysler has serious issues as the vehicle got older, why??? well, the alternator still used segmented armature and as it wore, the output was spiked and that introduce hash which overwhelmed the system and made diagnostics hard until they found out the issue, so now the alternator has slip rings.
bad grounds and iffy connection are a common issues. today, data logging is most important but most do not have the $$$$$ equipment so shops make $$$$$.
The map sensor gets 5 volts from either the ICM or ECM..
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,703
Likes: 7,887
From: poway
Yeah, Like bad 5 volt supply.. Either connection or source.
Thread Starter
|
Cruiser
Joined: Aug 2012
Posts: 128
Likes: 22
From: West Michigan
Understood. Wiring appears OK on a visual inspection, sensor showed up today so I'm going to install it and see. Even if it is a power supply problem the sensor has 150k miles on it so it won't hurt to have a new one.
I have the multimeter but am working alone and some of the recommended output checks (specifically readings at variable throttle settings) would be easier done with two people.
Appreciate all of the advice, I will report back as to what the problem turns out to be.
I have the multimeter but am working alone and some of the recommended output checks (specifically readings at variable throttle settings) would be easier done with two people.
Appreciate all of the advice, I will report back as to what the problem turns out to be.
Last edited by GlennJ; Nov 26, 2025 at 06:01 PM. Reason: More detail
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,703
Likes: 7,887
From: poway
Understood. Wiring appears OK on a visual inspection, sensor showed up today so I'm going to install it and see. Even if it is a power supply problem the sensor has 150k miles on it so it won't hurt to have a new one.
I have the multimeter but am working alone and some of the recommended output checks (specifically readings at variable throttle settings) would be easier done with two people.
Appreciate all of the advice, I will report back as to what the problem turns out to be.
I have the multimeter but am working alone and some of the recommended output checks (specifically readings at variable throttle settings) would be easier done with two people.
Appreciate all of the advice, I will report back as to what the problem turns out to be.
Years ago a friend has an EVO FXR that was having electrical problems with over 100K one it. We split the harness cover at the steering neck and started pulling. We found 3 wires that had the copper wire shredding inside.. On was pretty bad but the others had enough overlap that they still made contact, sort of.
Based on the wiring diagram, the only other sensors are intake temp and 1/2 of the TGS power. You want to check sensor voltage 2, sensor ground 2 and the Map signal wire.
It may be the TMAP. It may be grounds to the ECM..