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Dodge Repair/intermittent shutdown problem: 3.3L '99

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QUESTION: 99 Dodge Caravan 3.3L 4 spd

I have asked this question before. This van keeps on doing this intermittent shut down problem. The engine will shut down; if the engine is at cranking speed, it will restart immediately by itself and if not at cranking speed, I need to stop, put the transmission in N or P and then it will restart immediately (except at two occasions, when it took few cranks to re-start). This problem is going on since April 2014. I cannot isolate any pattern! It can happen at slow speed or on the highway. It can happen while the engine is cold or hot. Following is the only available info that I am sure of:

1) Whenever it shuts off, only the 'Alarm Set' and 'Service Engine Soon' lights come on on the dashboard. Both go out irrespective if the engine restarts by itself or not.
2) It can happen few times in a day or even in a single trip to run few errands around town. Or it may not happened for few days! The problem is increasing in frequency.

I have checked wires for damage, cleaned throttle body, cleaned EGR valve, check vacuum hoses, cleaned ECM contacts, cleaned almost all ground points.

What to do next? There are no warning lights so I am not sure if a scan will help. Should I get one?

ANSWER: Hi Shafique,
Try manipulating the ignition key up/down, side to side, in and out while driving to see if that might provoke the shut down due to a faulty ignition switch.
Other than that, a fault code readout is probably worth doing to reveal another possible reason to this problem. I would not recommend buying any parts/repairs until you do the fault code readout. Tell the any numbers and we'll go from there.
PS Please read the PS below and respond to it.
Thanks,
Roland

---------- FOLLOW-UP ----------

QUESTION: I have already tried the ignition key; nothing happens. I am not able to reproduce the problem by any means; tried wiggling wires/vacuum hoses under the hood; nothing happens.

I did a fault code readout today; NO codes stored. The guy gave me a printout, that mentions Downstream name, the value and its units. For example, MAP volts are 0.29 volts. The only thing I see weird is that both 'Current CKP State' and 'Current CMP State' is LOST.

What do you suggest?
Thanks.

ANSWER: Hi Shafique,
I haven't seen the terms CKP nor CMP so I wouldn't know what to make of their "state" being "lost". These may refer to the crankshaft position sensor and the camshaft position sensor but I have not seen a fault code that describes them as "lost". Either of those sensors, if their signals were "lost" would cause the engine to falter or die. Those would be fault codes 0320 and 0340. Both rely on an 8 volt supply wire that is orange in color and comes from pin 44 of the powertrain control module. You could check that wire for possible damage.
The MAP voltage being a 0.29 volts is very suspicious. It should read some where around 4.6 volts with the key in th run position and then when the engine is warmed up and running at idle it should read around 1.5 volts. That 0.29 should only be measured if the engine was operating at very high altitudes above the sea level (that reading 0.29 would be appropriate for a mountain top location!).
It may thus be worthwhile for you to replace that MAP sensor. It is located on the intake manifold very close to the power steering pump. Check the voltage of the violet/white wire which should be about 5 volts with the key in the run position. Then measure the voltage on the dark green/red wire again with the key in the run position where is should be somewhere between 4.4 and 4.7 volts. Then start the engine and notice the voltage drops to less than 2 volts. Measure the voltages between those wire and the third wire which is black/light blue. Access the wires is by means of fine straight pins inserted through the wires' insulation so as to touch the internal metal conductor inside the wire.
Let me know what you find.
Please do another rating and nomination.
Thanks,
Roland


---------- FOLLOW-UP ----------

QUESTION: I searched the net for CKP and CMP and yes these relate to the two sensors. These sensors are supposed to be present or lost during the diagnostic process, when and why, I do not understand. But lets leave those aside as most probably they are not causing the problem.

More importantly, I tested the MAP as you instructed. The voltage between violet/white and black/light blue is 5 volts and between dark green/red and black/light blue is ~4.5 volts, when the key in run position. Then once the engine is started, the voltage between dark green/red and black/light blue wires drops to ~1.4V BUT the voltage between violet/white and black/light blue stays at 5V. Does it mean that the MAP sensor is definitely bad? In that case, is it possible to clean it or just replace it?

It is worth to mention that earlier I gave the MAP voltage just as an example from the diagnostic report to you. There are other sensor voltages in the report as given below.

TPS volts 0.29
Upstream O2S volts 0.29
Dnstream O2S volts 4.70
Eng Coolant Temp volts 4.70
Target Charging volts 0.93
Knock sensor volts 0.00
Fuel Level sensor volts 0.00
S/C switch volts 4.70

Please let me know if anything is off the chart and what should I do with the MAP sensor.
Thanks

Answer
Hi Shafique,
The MAP sensor voltage appears to be appropriate at idle. It wasn't clear to me what were the conditions of operation when it read 0.29 (might that have been shortly after the engine was revved up and was slowing down, in which case that too could be OK?). So I would not change out the MAP sensor.
The upstream oxygen sensor is a bit low in its voltage reading but not enough to do anything. The ideal value would be 0.5v. But the downstream oxygen sensor appears to be shorting out between the operating voltage 5v source and the signal wire. That should be checked out and replaced if you don't find a correctible short between the four very fragile wires between the tip of the sensor and its plug.
So that downstream sensor is all I can point you toward, other than to perhaps check the orange wire that supplies the 8V to the cam and crank sensors just in case that is flakey and thus causing the "lost" report (though I too am not familiar with what that implies). Clearly if that 8v supply were not solid that could cause momentary shutdowns.
Thanks for continuing to rate and nominate me for volunteer of the month.
Roland  

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Roland Finston

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Get a Free Fast answer to your repair question about a Chrysler/Dodge/Plymouth car, minivan, SUV, or truck. Problems with electronically controlled engines and transmissions as well as body wiring problems are my specialty. This free troubleshoot advice forum helps you diagnose faults, minimize repair costs or do-it-yourself.

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I was voted "Top expert" from 2010-2015 here at AllExperts, and have answered 20,000+ questions.

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Five decades as a 'do-it-yourselfer' on domestic and imported cars

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Yahoo Autos Group called The Chrysler Lebaron Club (co-moderator)

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Degrees in Physics/bruised knuckles.

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"Top expert" of 2010, 2011, 2012, 2013, 2014, and 2015 here at Allexperts. Quickest "average response time" at Allexperts (currently no. 1).

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