Old starter causing P340 cam shaft sensor error - JeepForum.com
 
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post #1 of 8 Old 12-07-2019, 10:05 PM Thread Starter
Zippyman1962
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Old starter causing P340 cam shaft sensor error

Can a starter cause a p340 code? My 2005 TJ 4.0 manual Jeep only throws the p340 code when sitting overnight with temperatures below 40deg. I have replaced the cam shaft sensor 3x (Dorman, crown, then MOPAR), oPDA, harness connector, had the PCM flashed. The circuit integrity is excellent
My thinking is that the turn over is slower when cold cranking than when the temperature is above 50deg. Could the PCM be looking at the cam shaft signal based on expected timing? I scoped the signal and it is a good 5V square wave, the OPDA was synchronized during its replacement.
As soon as the engine warm I restart it and it clears the code and runs fine (was in limp mode).
My next steps are to replace the speed sensor (uses the same 5V) then the starter, the the PCM
Any help would be appreciated

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post #2 of 8 Old 12-08-2019, 01:21 AM
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P0340-CAMSHAFT POSITION SENSOR CIRCUIT
When Monitored: Engine cranking/running. Battery voltage greater than 10 volts.
Set Condition: At least 5 seconds or 2.5 engine revolutions have elapsed with crankshaft position sensor signals present but no camshaft position sensor signal.

POSSIBLE CAUSES:
INTERMITTENT CMP SIGNAL
INTERMITTENT CKP SIGNAL
(F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE
(F856) 5-VOLT SUPPLY CIRCUIT OPEN
(F856) 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
(K44) CMP SIGNAL CIRCUIT SHORTED TO VOLTAGE
(K44) CMP SIGNAL CIRCUIT OPEN
(K44) CMP SIGNAL CIRCUIT SHORTED TO GROUND
(K44) CMP SIGNAL SHORTED TO THE (F856) 5-VOLT SUPPLY CIRCUIT
(K900) SENSOR GROUND CIRCUIT OPEN
CAMSHAFT POSITION SENSOR
PCM

I wouldn't consider the starter as being the cause of this problem. With the issue being temperature related, I'd lean toward a gap/tolerance issue with the cam sensor and tone ring or possibly an electrical connection problem that clears up as things expand when the engine bay warms up. In addition to checking the list of possible causes above, if you have the time to do some experimenting maybe consider warming up suspect parts with a heat gun prior to engine start to see if that prevents the code being thrown.

2000 TJ SE
2005 LJ Rubicon
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post #3 of 8 Old 12-08-2019, 07:00 AM
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an 05 with this issue - always a problem as the OPDA used these yrs @(05-06) were problematic.

Do you have the origional CMP*? it is common that the OEM will correct this as the replacement CMP's even the replacements from jeep are not as comparable with system as the original.

thats all I got to add sorry

* just the sensor not the whole OPDA

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #4 of 8 Old 12-09-2019, 12:03 PM Thread Starter
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Quote:
Originally Posted by jtec View Post
an 05 with this issue - always a problem as the OPDA used these yrs @(05-06) were problematic.

Do you have the origional CMP*? it is common that the OEM will correct this as the replacement CMP's even the replacements from jeep are not as comparable with system as the original.

thats all I got to add sorry

* just the sensor not the whole OPDA
Thanks for the response JTEC; I do have the original CMS installed in the replacement OPDA unit. There was no change in the cold crank behavior regardless of which 3 sensors I used.

I still have the OEM OPDA; what I plan to try is reducing the CMS’ mounting base thickness by 1 or 2 mm (based on measurements of the sensor face and notched disc). I’ll use the Dorman sensor so to preserve the original (I can’t confirm if it is a MOPAR replacement or the OEM). I’ll see where that takes me.

I believe the starter is the original; I know the engine turns over slower when the cold crank issue occurs and that the CMS signal is always present and is 5V square wave (looks the same as when at temp) just has a slower frequency (timing)
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post #5 of 8 Old 12-09-2019, 12:29 PM Thread Starter
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Thanks for the response MukLuk; even though the CMS signal is always present and the 5V square wave signal looks the same as when cranking at temp or cold (just has a slower frequency / timing) I believe the critical gap spacing of the tone ring and CMS face needs evaluating.
I still have the OEM OPDA; what I plan to try is reducing the CMS’ mounting base thickness by 1 or 2 mm (based on measurements of the sensor face and notched disc). I’ll use the Dorman sensor so to preserve the original (I can’t confirm if it is a MOPAR replacement or the OEM). I’ll see where that takes me.

I appreciate the K code definitions. I previously ruled those conditions out early on. Circuit integrity and sensor integrity are fine. If the 5V was collapsing or shorted to ground the speed sensor would also fail; I ohmed the source, ground, & signal paths- all are good. I have also scoped the signal, 5V, and ground with accessories ON, during, and after cranking - everything is solid and square (0v to 5v). Only difference is the timing.
At temp each notch is -0.8ms, when cold the notch is - 2.68ms. That’s over 3x slower engine turn over rate when cold vs when hot. In that condition it takes -10 seconds to start.

I believe the starter is the original; I know the engine turns over slower when the cold crank issue occurs and that the CMS signal is always present and is 5V square wave (looks the same as when at temp) just has a slower frequency (timing)
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post #6 of 8 Old 12-09-2019, 03:18 PM
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AS I mentioned I don't have much to add-
I do try to keep up as an answer is sought.

I see a TSB for a reflash, not much but wanted to add.
Attached Files
File Type: pdf p0340.pdf (121.8 KB, 1 views)

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #7 of 8 Old 12-09-2019, 05:30 PM Thread Starter
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I forgot to add to my reply that I did several test with a heat gun; initially I suspected that the PCM input had developed a hair line fracture in the input signal path (P2 pin 34) or maybe a cold solder joint. I heated the PCM to several degrees above ambient all around P2 and the PCM mounting plate. Didn’t make any difference. By that time I had already installed a new inline harness plug, a new OPDA and CMS sensor. I didn’t heat the starter
This weekend I will use a thermal imaging gun to heat several areas based on normal driving temps And see if thee are any correlations.

Cheers
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post #8 of 8 Old 12-09-2019, 05:54 PM Thread Starter
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Quote:
Originally Posted by jtec View Post
AS I mentioned I don't have much to add-
I do try to keep up as an answer is sought.

I see a TSB for a reflash, not much but wanted to add.

Thanks Jtec
I had the PCM flashed last month to the last update as there was a 2009 CMS and CKS sync issue flash. I didn’t know if my PCM had any flash updates as I bought it in 2014.
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