car wont start after failed attempt of jumping low pressure switch - Honda Civic Forum

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car wont start after failed attempt of jumping low pressure switch

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Old 09-08-2017
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car wont start after failed attempt of jumping low pressure switch

help!!! i tried jumping the low pressure switch through the red wire sending 12v directly to it and the vehicle immediately shut of now it wont start
and there is no communication at the OBD2 connector. Is the computer now fried? Or is there a fuse or relay I'm simply missing? All fuses that I have found check out fine.
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Old 09-08-2017
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Re: car wont start after failed attempt of jumping low pressure switch

anyone?
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Old 09-08-2017
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If you think a good mechanic is expensive, try hiring a bad one
 
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Re: car wont start after failed attempt of jumping low pressure switch

What kind of car exactly?
I see where you are in the Bahamas?...What country is the car from?
Year/model/trim/engine


Where is the plug you jumped?
How many wires are on the plug you jumped?
What colors are each of those wires?


You already know that what you did shut the engine down, and no communication from the computer is a VERY bad sign.
Have you checked all fuses in both fuse boxes?

Disconnect the battery, wait 15 minutes, reconnect and recheck?
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Re: car wont start after failed attempt of jumping low pressure switch

yes im from the bahamas and its a 2007 honda civic coupe ex 1.8
U.S model

i put 12v to the red wire on the low pressure switch in an attempt to check my compressor. there was three wires one green one black one red, the red is what i i tried to jump. checked all fuses and relays all seems good. after putting the 12v to the red wire the vehicle shut off immediately and only cranks but no start.

1.no communication at OBDII port
2.fuel pump isn't priming any more
3.vehicle not starting.
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Old 09-08-2017
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If you think a good mechanic is expensive, try hiring a bad one
 
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Re: car wont start after failed attempt of jumping low pressure switch

Ok...a quick check of a factory wiring diagram tells me a few things...
I doubt what you did would blow any fuses....but much worse.


1, that's not a switch at all, that is a real pressure sensor that goes directly to the PCM (engine and transmission computer)

2, if the 15 minute power down (battery disconnect) and 'reboot' does not change anything, that means the PCM is, indeed, ruined. (I might try this more than once just to be sure....leave doors open during the battery disconnect period too)

3, the red wire is VCC6 (5v reference supply to more than one sensor) in the PCM.....and you probably damaged that 5v regulator in the PCM when you applied battery power to the 5v line. (there is another thread somewhere in this forum where someone else did a similar thing on a similar year car, ruined the PCM by jumping wires for that AC pressure sensor without knowing what he was doing)

4, after the expensive PCM is replaced and the immobilizer system is programmed to get the engine to run again (more $$) .......you will still have the original AC problem you started with

5, the AC problem is probably NOT related to the pressure sensor you were messing with. There are several fairly common electrical and mechanical issues, but that sensor is not an expected issue IMO.


Sorry man, it's not looking good at all.
HTH

Last edited by ezone; 09-08-2017 at 11:31 PM.
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Old 09-08-2017
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Re: car wont start after failed attempt of jumping low pressure switch

thank you very much for this information. i will further update you tomorrow after i drain the battery and see what happens. worst case i'll have to buy purchase a new pcm and have it programmed.
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