Map Sensor

[Rick]

2003 Dodge Grand Caravan Sport 3.3L V6

I’ve recently pulled a few codes, one being the MAP Sensor (P0106) and the Throttle Position Sensor (P0122). I pulled the MAP connector from the sensor. Ground has continuity, with the key on I get 4.8v supply. Here is the thing, according to the wiring diagram (provided) 5V supply should be coming from pink/yellow, but there is no voltage reading on that wire. The 4.8v reading is on the violet/brown wire. I’ve checked this multiple times. Then, when I plug the connector into the sensor, I get only .17V on the violet/brown and no voltage on the pink/yellow while probing the connector. According to what I’ve read the 4.8v reading should remain until I turn the engine over where it drops to 1V (I think). I haven’t checked into the TPS yet, just wanted to get some thoughts on this. Thanks.

Attachments:

• pinouts.png

Topic

[Mike]

You should get 5 volts from pin 3 with the KOEO. Also, you should not have power on the ground wire.

[Rick]

No, there isn’t power on the ground wire, I was just stating that it has continuity. What is happening is that there is 5 volt supply on wire 1, which is incorrect according to the diagram. There is no voltage on wire 3. So I’m thinking that somehow the connector is wired incorrectly, I can’t think of any other reason.

[Rick]

So, I removed the connectors to the PCM and checked the TPS and MAP sensor. I read 3.4v on the 5 volt supply, ground, and PCM signal wires for both sensors. I assume that I must have a short somewhere, because those sensors shouldn’t be reading anything if the PCM is not connected. Anyone have any advice on tracing a short?

[college man]

I would ohm the wires from the sensor back to the pcm.

[Walter Cheryba]

OK, so are you saying you NOW have 3.4V on the ground wire (PCM disconnected) where there was NO voltage reading on the ground (only continuity) BEFORE you disconnected the PCM? :unsure:

[Rick]

Yes, sunset, exactly.

[Walter Cheryba]

OK, here comes the seemingly dumb question-does the voltage situation reverse itself if you reconnect the PCM? If it does then I’d get a good nights sleep, pull out the power probe, the wiring diagram and start tracing circuits. Wish I could offer more. do you know anyone that subscribes to Mitchell All Data or a Snap-ON diagnostic service? If so they might be willing to input your info and find a common recurring short location.

[Rick]

Those services sound awesome, I might have to look into that. If I reconnect the PCM the original voltage situation presents itself with 4.9v on the signal circuit (to PCM) and no voltage on supply and ground. But just a few minutes ago I disconnected the TPS and turned the engine over. When I accelerated the engine did not stall (which has been my issue every time I hit the gas and open the throttle). I plugged it back in and tried again, instant stall. So could a bad TPS be causing these wacky voltage readings, the engine stall, and the codes?

[Walter Cheryba]

Now you’ve twisted things up! I’m still leaning towards a short of some type. Try this for confusion, disconnect the harness from both the TPS and the PCM and see what the readings are. Sanity tells me that you should have no voltage readings and if you do then there is definitely a short and you are back to Collegemans suggestion to ohm the circuits. The TPS could be faulty AS WELL but I’m not there yet. Remember short circuits caused by a rubbed through harness against some part of the body can cause ghost like or random situations.

[Author]

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