Check Engine Light

ALEX.PERAULT

MEMBER
1997 SATURN SL2
4 CYL
AUTOMATIC
133,506 MILES

I bought a used 97 Saturn SL2, and within a week of driving it, the check engine light came on. I took it to get diagnosed and it came back with P0105 MAP/BARO circuit malfunction. I also noticed that there were fuses missing for the horn. I replaced that and within a minute, smoke just started to pour out (?). I bought a new MAP sensor and cleared the code. The next day the code came back. After about a week of the code being there I put the car in to a shop, and they told me that the temp sensor was shorted and replaced the sensor and some wiring around it and they also replaced the horn. I drove it home and the next day on my way to work, the light came back on. I have spent hours researching a possible cause but cannot seem to find it. Can you help?

3 Replies

WRENCHTECH

MECHANIC
20,761 POSTS

There are many possible causes of setting a MAF code. It can be a problem with the sensor, the PCM, any related wiring, the air intake or even the exhaust system. It needs to be diagnosed by a competent technician.

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Sunday, February 27th, 2011 AT 7:54 PM

SATURNTECH9

MECHANIC
30,869 POSTS

Hey wrenchtech just wanted to add to your answer. Code p0105 is for the map reading's compared to the throttle position sensor are skewed. Is your car setting the same code P0105 or a different one?Here is the code description etc.
The PCM has internal tables that compare MAP sensor values with TP sensor values. The MAP sensor is a variable resistor that responds to changes in intake manifold pressure. The voltage ranges from 1.0-1.5 volts at idle (high manifold vacuum) to 4.0-4.5 volts at wide open throttle (low manifold vacuum). The TP sensor is a potentiometer which responds to changes in throttle plate angle. At a closed throttle position, output of the sensor is low (approximately 0.5 volts). As the throttle plate opens, the output signal increases so that at wide open throttle, the output will be high (approximately 5 volts).

DTC PARAMETERS

DTC P0105 will set if MAP or TP value is out of range greater than 2 seconds when:

* No P0107, P0108, P0122, P0123, P0506 or P0507 DTCs are present.
* RPM between 1600 and 4000.
* RPM change is less than 100.
* Steady EGR command.
* A/C command is unchanged.
* IAC change is less than 10 counts.

DIAGNOSTIC AIDS

This DTC will set if either MAP or TP is out of range. To distinguish which one failed, review malfunction history information and attempt to duplicate the conditions.

Check sensor and PCM connection for corrosion.

Check tightness of female terminal grip with a spare male terminal.

With the engine Off and key On, the map reading should be the same as the barometric reading because manifold pressure is equal to atmospheric pressure (no vacuum - high voltage). Comparing this reading to a known good vehicle with the same sensor is a good way to check accuracy of a suspect sensor. Readings should be within 0.4 volts.

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Sunday, February 27th, 2011 AT 8:55 PM

WRENCHTECH