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The map sensor circuit appears to be very simple; 3-wire sensor = power, ground, and signal. With your electrical testing, you have concluded that you have an open in the circuit and that the open affects all wires to the map sensor. The open may appear as a loose connection, corrosion, cut or disconnected wire. Trace the wires to the best of your ability to locate the open. Once you locate the open, perform the appropriate wire repair. If unable to locate the open, you have two options: pull the entire MAP sensor harness to the ECM or run your own wires directly from the ECM to the map sensor.
*DO NOT APPLY YOUR OWN POWER TO THIS CIRCUIT (i.e. ohm testing for continuity) BEFORE ISOLATING THE MAP SENSOR FROM THE ECM AS YOU COULD FRY THE COMPUTER!!!
The following schematic shows the simplicity of the circuit; however, fails to identify which wires do what.
Be advised that you may not get a reference or signal voltage unless the key is in ‘RUN’ or the engine in actually running.
https://www.youtube.com/watch?v=iE1ORHc4r7c
I would test a known good working honda to identify what wires are performing a particular function, or call up the honda dealer. Or, maybe someone on this forum my know… even Mr. Car Guy could chime in here as a Honda guru. 🙂
I would lean away from a ECM failure as all other computer controlled components are functioning properly… but all things are possible in the world of automotive.
That said, test for reference voltage directly from the ECM to rule out this possibility.
iwas thinking the same to cuz I check the volts coming straight from the esu and no volts I put 3 map sensor so I think is the ecu
Honda MAP sensors hardly ever go bad, same goes for the PCM’s. If however your engine is running poorly, it can set a MAP sensor code. If you’re experiencing engine performance problems, I would address those first and then check to see if the code returns. More info on that here.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues
It could also be a wiring or connector problem as pointed out but only as a last resort would I look to the PCM for a problem.
Sorry for bringing back up from the dead, but wanted to share my experience in hopes it may help someone in the future.
1998 Civic EX M/T (bone stock). Had very strange driveability issues that was due to an internally and partially broken wire to the MAP. Not sure which wire it was though since I just replaced all 3 wires in the affected section (about a 6 inch section just after the point where the MAP wiring is first loomed together with the IAT wiring in the engine bay). Visual inspection of the wires suggested they were perfect, but when I bent the MAP wiring in this area, the car would sputter and sometimes die. This was a pretty insidious root cause imho because I actually tested the MAP (and a bunch of other things on the ignition and fueling side along with cam timing), and it was fine (all fine). Anyway, here were the symptoms (or lack thereof) I had:
* No DTC’s or CEL’s… EVER
* Idle was very smooth and steady @ ~750 rpm (for real, it was butter smooth)
* Below 3K or 3.5K (depending on the mood of the car that day), the car ran very smoothly
* Above 3K+, car would hesitate/jerk @ part throttle, full throttle, and whether there was load or not on engine (ie, happened even in neutral)
* At first, car would fight its way through the hesitation/jerking and @ ~4K would smooth back out. Issue got worse though, and eventually car would have major problems just getting past 3K even after several seconds. A couple of days before I discovered the damaged wiring, car automatically returned to the first state of fighting through hesitation and smoothing back out @ ~4K
* Strange one: Had platinum NGK plugs in car and swapped in some copper NGK’s, and car ran even worse. Idle and driveability below 3K were still perfect, but issues above 3K were magnified. Put platinum plugs back in and car reverted to less crappy driveability. This convinced me the root cause must be some weak link on the ignition side but alas no…
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