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1999 dtc340 problems

1K views 14 replies 3 participants last post by  disc42 
#1 ·
I have a 1999 intrepid 3.5 that is showing a dtc 340 code.I have replaced the cam and crank sensors and the connector to the cam sensor.I have checked the 8 volt power to the sensors and checked continuity on ground and sensor output.All seem to be good.The only thing I can,t confirm is the 5 volt signal from the sensors to the pcm because I don,t have a scope.The engine cranks and runs but rpm rises and falls and injectors and coils dont fire for about 10 seconds when key is turned to start.Also I can,t clear the 340 code.The car runs good until you try to accelerate too hard then it bogs down until you let off on the pedal.Any thoughts would be appreciated.
 
#2 ·
When replacing the cam sensor, you have to be sure to leave the paper spacer on the end, otherwise the sensor will be damaged. Also, if you used aftermarket sensors, that could be the problem.

Try it with the cam sensor disconnected. It won't run above 2500 rpm like that, but if it otherwise runs OK with it disconnected, that will narrow the problem down to the cam sensor.
 
#3 ·
The injectors and coils not firing suggests that the ASD relay is not being energized by the PCM for some reason - the injectors and coils both get power thru that relay. Not sure why the PCM is not energizing the ASD relay if that's the problem. I believe the FSM lists the things that the PCM looks at to decide the energize the relay.

The bogging under acceleration could be fuel pump (low pressure) or fuel filter (partially clogged) issues.
 
#4 ·
I replaced both sensors with made in usa sensors.Airtex Wells and Standard Motor Products both are reputable aftermarket suppliers and yes I left the paper spacer on.THe ASD relay does energize when you turn the key on for one second but doesn,t come on for about five seconds when starting it.I have noticed the aftermarket sensors don,t have a very strong magnet like the oem sensor.I switched the ASD relay with another one and no help.
 
#5 ·
Aftermarket cam and crank position sensors for these cars have been shown to be problematic. No guarantees, but often when aftermarket ones are replaced with OEM ones, problems like this go away.

(I can tell you that the aftermarket O2 sensors for our cars are absolutely incompatible - they have a major and documented electrical design flaw, but for some reason, the manufacturers are either ignoring the problem or simply aren't paying attention and continue to sell O2 sensors that are seriously problematic - the exceptions being NTK/NGK and Denso. OEM, NGK, or Denso only for O2 sensors for these cars. Based on repeated bad experience with aftermarket cam and crank position sensors over many years by many people on the LH car forums, it is suspected that they don't necessarily have a design flaw like the aftermarket O2 sensors, but have poor electrical tolerances and reliability/quality issues - so OEM only.)

...THe ASD relay does energize when you turn the key on for one second but doesn't come on for about five seconds when starting it...
When starting, the PCM keeps the ASD relay off until it is satisfied that it is getting good engine sensor signals, then it energizes it, and like magic, the engine starts. This would explain the delayed start, and, again, points to a marginal sensor issue. If it were me, I would replace the sensors with OEM and see where you are. YMMV.

Again - fuel pump or fuel filter issues may be at play. I can't be sure which (sensors or fuel pump) is the major player with your problems.
 
#6 ·
I,m going to yank a cam sensor off a 3.5 at You Pull It and see if that does the trick before I spend 65.00 for oem and can,t return it because it electrical.Thanks for the info.I,ll report back after I try that.Maybe in couple of days when this crappy weather goes away.
 
#8 · (Edited)
Oh - don't forget to put some kind of tape or paper on the tip of the used sensor so it doesn't get damaged. Correct thickness is about 0.030" (0.8mm, about the thickness of two matchbook covers according to FireM/Bob, or 4 regular 3x5 cards). Push the sensor down in the holder before installing so it will self-adjust when you install it. You may already know, but the idea is that the spacer will get knocked off soon after starting the engine.
 
#11 ·
P0112-INTAKE AIR TEMP SENSOR VOLTAGE LOW

When Monitored and Set Condition:
P0112-INTAKE AIR TEMP SENSOR VOLTAGE LOW
When Monitored: With the ignition on and battery voltage greater than 10.4 volts.
Set Condition: The Intake Air Temperature (IAT) sensor circuit voltage at the PCM goes
below 0.8 volt.

POSSIBLE CAUSES
IAT SENSOR SIGNAL CIRCUIT SHORTED TO GROUND
IAT SENSOR SIGNAL CIRCUIT SHORTED TO THE SENSOR GROUND CIRCUIT
IAT SENSOR
POWERTRAIN CONTROL MODULE
WIRING HARNESS INTERMITTENT

On Pre-2002 3.2/3.5 cars the Intake Air Temperature Sensor is combined with the MAP Sensor in one unit. It's on the Drivers side of the Upper Intake Manifold or Plenum.
 
#12 ·
Here's a picture of it on my 2000 R/T. It's above the yellow Transmission fluid dipstick handle in the picture.

 
#13 ·
Betting that's a clue to your P0340 code. Several of the engine sensors but not all use a common voltage source from the PCM. When the wiring to any one of them shorts out it echoes across the others.

In your case it seems like it's the ground circuit that might be the common issue.
 
#15 ·
Well I,m back with the latest update.Went to the junk yard and pulled the cam sensor and map/air temp. sensors.After install no difference at all.Just to review symptoms no spark to injectors or coil packs for approximately 5 seconds,then cranks and rpm high at 1500,rpm comes down slowly to 1000 after about 5 min. with fluctuations up and down.If you put it in gear rpm drops to 750 and will remain there after returning to park.I,m thinking pcm.Will the one from 1999 Concord i removed sensors from work on my 1999 Trep.
 
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