tsarang

Guys, I am getting the dreaded P0340 code. My car (96-ls400) would start and then the RPMS would go to 2000 then 1000 back and forth several times and after few seconds it will die. same thing when I restart.

If i give throttle the engine will not die but The car shudders and the rpms still keep on going up and down. eventually if I let the throttle down the engine will die.

Here is what I have done till now.

a) traced wires for shorts. They checked out ok.
b) Tested resistances for both camshaft sensors and the crankshaft sensor, all came out to be within the right specs.
c) tested ignition coil resistances, came out to be within the right specs.

Do you think my timing is off?.

My car was running perfectly, this only started with the below 20F tempratures we are getting in Florida. do you guys still think it is the sensors going haywire because of the cold?

Help definately needed from the gurus out there. Please Help

Thermactor

iTrader: (1)

did you check the continuity of the wires on both the sensor end and the ECU end? A mouse might have eaten the wire or something.

LiCelsior

iTrader: (32)

im looking on Alldata and i dont see a P0340 for the 96 LS400.

tsarang

Thanks for your kind reply, Thermactor I will follow your suggestion and trace the continuity of the wire to the ECU

Thanks LiCelsior, I had an OBDII diagnostic tool to get the code out.

Banshee365

I posted a lengthy reply on the other forum that you posted the same question on. Let me know how things turn out.

tsarang

Hi Guys,

Banshee365 Thanks for your excellent feedback.

Here is the complete story. My LS has been working perfect since last year, no complains, . I was parking at the local walmart with tempratures down to 16F. Suddenly it starts acting up and showing the symptoms above. I was able to limp it back home, after that the rpms would never stabilize the car would die in a few secs after starting.

I had a issue during last years winter when the car would start and blow out white smoke. everybody had said it was a shot gasket but it turned out to be a bad ECU. when we opened the ECU we saw acid eating up parts of the circuit and knew there and then, that it was an issue. Changed ECU and the car chirped like a bird!!! as i said it was perfect till that fatefull day at Walmart!!.

I could never get to test the car at higher temps, because currently the highest
temp here in tallahassee is 40F (in Florida, can you believe that!!!)


I am pretty sure the cold weather is the cluprit, since I am not getting any feasable results
by testing sensor specs, I am going to try something else.

I will start by taking a small handy heater and directly heating the sensors in the following
manner.

a) ignitions coils
b) camshaft sensors
c) crankshaft sensor
d) IAC.
e) eventually if I dont get any concrete results I will have a bigger heater to heat the
whole engine and see the results.

I am betting that it is going to be one of them. I have ordered a,b and c sensors,
i want to replace them anyways as preventative maintainence.

I am excited and have a long day ahead of me, I will update results.


Wish me luck Guys, Again Thanks for all your inputs

tsarang

ok guys i am back, here is what I managed to do today

a) Heated car so that it could start up without dying

car would run very bad with shaking, but idle (RPMS) got stable and it didn't shutdown. If I up the throttle, car would die.

I got P0340 now with "TRAC" light on and Off and sometimes (intermittently) p0300 (misfiring all cylinders) code.while idling.


b) Tried a couple of things, Cleared codes before starting and

1) Since I had this flashing "TRAC" symptoms before (it was due to a bad alternator), at that time too the car ran like crap on a cue I removed the alternator and took it for a test to the nearby auto shop. alternator checked fine.

2) From my ordered parts (i had ordered two ignition coils. Two CAM sensors and one CRANK sensor), The auto shop received the
IGNITION coils today, CRANK and CAM are scheduled delivery on the 12th. I collected the coils and installed them. BUMMER didnt solve
my Issue.

3) Cleared codes before starting and disconnected CAM sensor, Driver side (bank 1)

Lo and Behold, Car stabilizes, there is occasional jitter but RPM is stable, I can now raise throttle without stalling or hesitation, idled car like this for about 5 min didnt shutdown. No sudden jerking or RPM changes. I was surprised!!! Shutdown Car and Went to next step.

NOW I am still lost why #3 would not send out any code!!!!. should detect BANK1 being disconnected!!!.

4) Cleared codes before starting and Reconnected CAM Sensor (BANK 1) and Disconnected CAM sensor (BANK2)

Car acted Like before, running bad, shaking, Idle ok. got the P0340 code.

5) smelled a rat in the CAM position sensor 1.

Just remembered I had taken the resistances for the sensors while cold. Now since the car was hot i decided to take them again. Guess what, BANK 2 stabilizes at a certain resistance while BANK1 keeps on fluctuating which was weird.

I then decided to test the voltages out of these sensors, since they generate ac voltages, These can be measured.
the minimum my meter could go down was 200V and the voltages generated by the CAM sensors are very small ~ 1-10V pulses.

I still decided to proceed, the meter was registering the voltages as in 0.001V or equal to 1v.

Here are the results of my test

BANK2 -- 1v-2v-3v-2v-1v-2v-3v-2v-1v-2v-3v ( Could make out this was cycling)
BANK1 -- 1v-1v-1v-2v-3v-2v-2v-1v-3v-3v-2v (this output looks like bad cycle, it was intermittently sending out same voltage instead of changed voltage)

looks like CAM sensor BANK 1 is a goner

I Cant verify this voltage test results with anything standard though, this is all guess work till now.

Will be waiting for my sensors to arrive and change CAM1 to verify my theory. I will let you'll know how it goes.

tsarang

Ok guys, Changed the camshaft sensor with a new one, Didnt help, same issue.

When I plug in the bank1 Cam sensor the car will not start at all. I can still make it rev by giving some more gas but it runs terrible, with bad gas smell and shaking and vibration. It will die as soon as I cut the gas. Once I disconnect the Bank1 sensor the car still runs bad (its not terrible, some vibrations) but it idles ok. I am lost at this one.

After this I was leaning on the crank sensor going bad but the car usually does not start at all if that happens, so that is counted out. also the resistance on the crank sensor checked out fine.

another thing I thought about is the timing belt jumping a teeth. How do I go about verifying that is not the timing belt?. will the car run atall with bad timing?.
any other ideas, leads??

I need your help guys/gurus out there. Thanks.!!!!!!

fourthmeal

The code didn't appear in the 96 texts but does in the '97. It is considered an "omission."

Inspect the sub harness where the crank and cam sensors join. The wire can become brittle and fail, and cause this code.

Also the reluctor wheel on the crank must be perfect, if there is a nick or scratch in it, it might cause this code.

Cam timing IS possible. But this car still runs very good even if only 1/2 the engine is running. SO, it is probably a mis-read from one of the Cam sensors.

Yotarip

Have you bothered to check out the ecu again. I'm willing to bet that it's the ecu again and especially if you replaced the original with a used ecu.

There are companies that will repair the ecu (if not severely damaged by the acid) for a fair price.

qewani1

http://www.obd-codes.com/p0340