2001 Oil Pressure Gauge None Responsive; MAP Sensor Low Voltage

[int3man]

O.K.  So planning on a 2,000 mile trip with the wife.  Oil pressure gauge has not worked since purchase.  Installed V2 Quadzilla.  Immediately threw Low voltage for the MAP sensor.  So the Oil Pressure Sender and the MAP Sensor Share the 5 volt reference voltage.  So I had it.  I took every thing loose that I could and then had a friends son come by and remove the rest of the harness.  Dropped it down in front of the axle so that I could reach the Harness.   The MAP sensor wires were twisted together and ran that way all the way to the bottom of the turn up for the ECM Plug.  The wires were longer than that joint so they ran forward with the balance of the wires.  So I continued to cut until I found the joint, it was 14- 18in forward of the ECM plug.  Cut the Joint out Stripped back some wire and measured 1,000 Ohms through the joint to either of the sensors.  So what does 5 volts drop to across a 1,00 ohms?  I know it is current related but don't know what the gauges draw.

 

Will Solder and Heat Shrink and rewrap the harness.  Good time to re-practice my lacing.  Crap I haven't laced a harness for 44 years.  Oh well Just like riding a bicycle.

 

Michael

Edited December 3, 2018 by int3man

[dripley]

I the FWIW column, I was getting the 237 code and my map sensor was dropping out. Turned out a splice I had in the 5v supply to the other sensors had worked its way loose. This was not the factory splice but a self inflicted splice near the ECM plug. I repaired that splice and MAP has worked fine ever since. I have no idea as to how they are related to one another but it worked. Just food for thought.

 

The splice you are going to do should work just fine, just be sure and seal it up good.

[int3man]

Boy do I fell like quite the fool.  Total tunnel vision.  Always remember there are 2 sides to a coin.

 

Or in this case there are three connections to the sensors.  Power +5 reference, signal out and Ground.  So I went after and found a bad connection to feed +5 volt power to my MAP and Oil Pressure sensors.  What I failed to look for, and will probably find, was a poor connection to GROUND for the same sensors.  So this week end I have to lean on friends to once again pull the loom out so that I can find and fix the poor ground connection.  Still no Oil Pressure gauge and MAP Sensor.

 

I'm reading +5v to the connector for the map sensor but that measurement was made from Battery ground to MAP plug.  I forgot to meter across the plug itself.  The sensors will not function without a Ground.

 

Back to it this weekend.  Feel like  a fool!!!

Michael.

Edited December 11, 2018 by int3man

[int3man]

O.K.  So I measured at the MAP Sensor.  I had 4.98 volts at the plug.  Pulled the Aftermarket MAP Sensor and the O-Ring was torn up.  Replaced it with the old Factory MAP Sensor and correct O-Ring,  and it worked once again, and I was able to clear the CEL. 

 

Ordered a Factory Oil Pressure sensor.  It also now measures 4.98 volts at the plug.

 

 

Michael

Edited December 16, 2018 by int3man