MAP sensor

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veljkovic@sbcglobal.net - 09 Nov 2008 15:13 GMT

I disconnected connector from MAP sensor and checked voltages on it.
Per Chilton manual, pin A is 5v supply, pin B is sensor which goes
back to PCM and pin C is ground.
First, I checked voltage between pins A & B. It is 0.10v (?!?),
between B & C it is 0.11 (?!?) and between A & C it is 0v (this is
OK).
Then, with ignition switch ON and car not running, I read 5.02v
between A & C (OK), 4.12v between B & C (!??! - shouldn't be 0v?) and
0v between A & B (?!? - shouldn't it be 5v?).
To repeat, I checked this voltages on connector side when MAP sensor
was removed.
Is it possible that some transistor died in PCM and jumped voltage to
sensor B? I need to clarify this before I purchase PCM.
Thank you.

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aarcuda69062 - 09 Nov 2008 17:59 GMT

In article
<fa4c93fa-484a-4a18-8a34-1673cdd0a142@c22g2000prc.googlegroups.com>,

> I disconnected connector from MAP sensor and checked voltages on it.
> Per Chilton manual, pin A is 5v supply, pin B is sensor which goes
> back to PCM and pin C is ground.
> First, I checked voltage between pins A & B. It is 0.10v (?!?),
> between B & C it is 0.11 (?!?) and between A & C it is 0v (this is
> OK).

You were working near fluorescent lights?

> Then, with ignition switch ON and car not running, I read 5.02v
> between A & C (OK), 4.12v between B & C (!??! - shouldn't be 0v?)

Inside the PCM, there is a pull down resistor connected to a 5 volt
supply which is connected to the MAP sensor input (pin B).

> and 0v between A & B (?!? - shouldn't it be 5v?).

Nope, you had 5 volts on both leads of your meter.

> To repeat, I checked this voltages on connector side when MAP sensor
> was removed.
> Is it possible that some transistor died in PCM and jumped voltage to
> sensor B? I need to clarify this before I purchase PCM.
> Thank you.

What you saw was normal, I wouldn't condemn a PCM because of that.

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