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Chrysler Repair/'04 300m:no spark, 5V supply shorted


Hello, Roland, do you remember this thread?  Just an FYI, the problem was a shorted wire to the Engine Temperature Sensor that sits in the front of the engine, just below and to the left (passenger side) of the Camshaft Sensor, right around the Thermostat Housing. I think the ASD was engaged, and I believe it was caused by the shorted Engine Temp Sensor wire.  Once the wire was fixed, the car started.  Kind of funny how the Engine Temp Sensor code never displayed, but it was shorting the 5vdc to ground (the 5vdc that all the other sensors were using).

Thanks again for your help, it was definitely a shorted wire!

No Spark, 2004 300M:codes 0335, 0340, 0122, 0129

I have a 2004 Chrysler 300M, 174K miles, and within the last 2K miles I replaced the timing belt, water pump and all tensioners/pulleys.  The 300M was purring along fine.  Until 3 days ago, when it wouldn't start.  I removed the timing cover and double-checked the timing belt, thinking that maybe the belt "stretched" and it jumped a tooth on one of the camshafts. No, that wasn't the problem.  I reassembled, then checked the fuel pump.  I could hear it run when I initially turned on the key. So I believe that is (at least) working.  But then I checked for spark on the front left cylinder (drivers side).  I removed the coil, then the plug, then turned the ignition.  No spark, and had my friend, a mechanic by trade, verify the "no spark condition."  This got his interest, so we checked for codes that are visible after turning the ignition on/off for 3 times, and leaving it on after the third time.  We got 4 codes to display at the Odometer window, the 1st being P0129, 2nd was P0122, 3rd was P0335 and the 4th was P0340.  We replaced the Crank/Camshaft sensors.  This did not fix the problem.  (We reset the computer codes after we installed the two sensors. We verified this be using the above mentioned on/off procedure and the car did not produce any codes, until AFTER we tried to start the car.  Then the 4 codes mentioned above returned).  We did not replace the TPI sensor because we believe this would not cause a NO SPARK condition.  (Yes?) That only leaves code 0129, and this item is located in the PCM, right?  I believe I have a bad computer, have I covered everything before attacking this ECM/PCM?

ANSWER: Hi Wade,
No, the 122 and 129 codes are for the tps and the map sensors, neither of which are located physically in the pcm. However, the one thing all four fault coded sensors share in common is a 5v supply voltage that they need to operate, and that does come from pin 29 of the pcm on a violet/white wire (it also goes to A/C pressure transducer). My thought is that the violet/white wire is either shorted to ground, or one of the sensors is shorting it to ground which of course would cause the 4 codes. So see whether or not you have 5v on that wire at any of the 5 sensors that is convenient. If not, then try disconnecting the plugs of the sensors one at a time to see if the 5v shows up on a violet/white at one of the disconnecting plugs that you monitor. I can tell you more about the harness connections of that wire from the pcm 29 pin if I am correct about the 5v not being available.
Please read the PS below and respond.

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

QUESTION: Would this also cause the no spark condition I am experiencing?  Has the computer shut down the car because it is not getting input from those four sensors?  In the morning I will perform the steps you recommended above and respond.  I will also honor your PS request above following the conclusion of our correspondence.  Thanks again....

ANSWER: Hi Wade,
Yes, if my theory is correct then the output from the cam/crank are missing entirely which means no spark will be generated by the pcm's not knowing what is going on with the engine rotational position, and also the signals from the other sensors are out of expectation (being 0v) which causes their codes and poor running if you did have spark.
So the pcm isn't shutting down the car, it just can't function without the signals from the rotational sensors. When you write back tell me which engine (L) you have, so if you can't find a sensor I can tell you where it is.
As to the PS request, you can either wait or do it after each answer that I send back. The website will 'count' towards a recognition of me up to 5 such nominations per questioner, so I will await your responses at your pleasure as we solve this situation.

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

QUESTION: Yes, I should have stated that in my first post...The engine is a 3.5L with Block Heater, 2004 Base 300M, 174211 miles.

The MAP sensor is on the left top of the engine near the spark coil for cyl 4.
The TPS is located at the upper side of the throttle body, and the A/C transducer is connected to the high pressure line of the compressor in the right lower front corner of the engine compartment (gray plug, 3-wires). Thanks for the ratings and nominations.

Thanks for that report, Wade. I am pleased that the cause of the short of the 5v supply to ground was found. It is not obvious why a short in one of TPS wires would cause the loss of 5v supply (it only has 2 wires: and sensor ground that is shares with a multitude of sensors, and a temp sensor "signal wire" that goes to pin 29 of the pcm). However it is the case that the TPS signal circuit also is based on that 5v supply, but in its case the voltage source is routed through a variable resistor to ground (which is the temp sensor). So normally the sensor signal wire won't flat out short the 5v to ground, only reduce it somewhat depending upon the coolant temp UNLESS that signal wire proper were in fact shorted to ground. So that makes sense. However when I simply read the wiring diagrams it was not spelled out that indeed the throttle position sensor does rely on the 5v supply, so if its signal wire is shorted it will thus short the 5v for all the other sensors I listed which then killed the spark signals.

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Roland Finston


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 have do-it-yourself experience (50+ years) and a library of 100 1982-2011 Chrysler factory shop manuals and 20 multi-manual Chrysler Corp. CD's.

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


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

Advanced degrees in Physics/bruised knuckles

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