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Pulled a code P0340.


PAUL T

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I have been trying to diagnose my mother-in-laws 2003 Deville. I finally got a code P0340 camshaft position sensor. Where is it located and how do I get to it and is there more than one on a 2003? I was getting P0171 & P0174 codes among others but I could not locate a vacuum leak so I cleared the codes and drove it about 15 miles and only the P0340 code came up. It was running great then it started surging some especially at idle. I need to check the wiring & plug before I get a sensor.

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DTC P0340

Camshaft Position (CMP) Sensor Circuit

On your car it is on the cam chain cover of the rear head on the passenger side. Figure from FSM:

2003_CMP_VSS_HO2S-1-1.png

  1. Camshaft Position (CMP) Sensor
  2. Vehicle Speed Sensor (VSS)
  3. Heated Oxygen Sensor (HO2S) Bank 1 Sensor 1

Usually these diagrams have a big arrow pointing toward the front of the car but not in this case. Troubleshooting begins with checking to see that there is 12 V supply voltage and ground at the sensor plug, then using a Tech II to observe what is happening with the engine running. If the plug is tight on the sensor and you can see 12 Volts on the RED wire (with the clip up, the right hand terminal) and a good ground on the PNK/BLK wire (center terminal), the sensor is probably bad. Avoid touching the connector terminal for the ORN wire (with the clip up, the left hand terminal) because it goes to the PCM and that circuit is static sensitive.

Connector end view:

2003_CMP_Connector.png

A. ORN, signal to PCM (avoid touching)

B. PNK/BLK, ground

C. RED, 12 Volts power (probably only when the key is on)

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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Good chance the 171 and 174 (lean bank 1 and 2) are related to a failing rubber intake coupler. The rubber bellows rot out and cause these 2 codes and surging. They always fail at the bottom where intake juices collect and rot the rubber out. They often look fine at first glance.

Fairly inexpensive dealer only part. About $20. The intake has to come off to replace. They all do it sooner or later...See red circle in the attached pic.

post-2-0-53002000-1388243359_thumb.jpg

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Thanks Logan, that is what I expected at first. I even sprayed throttle body cleaner around the bellow and there was no change in engine pitch. After I did that I cleared the codes and drove 20 miles and CES came back on and the P0340 was the only code. I drove it another 20 miles and nothing but the P0340 is appearing. I was just wondering if the P0340 would cause a lean mix.

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DTC P0340

Camshaft Position (CMP) Sensor Circuit

On your car it is on the cam chain cover of the rear head on the passenger side. Figure from FSM:

2003_CMP_VSS_HO2S-1-1.png

  1. Camshaft Position (CMP) Sensor
  2. Vehicle Speed Sensor (VSS)
  3. Heated Oxygen Sensor (HO2S) Bank 1 Sensor 1

Usually these diagrams have a big arrow pointing toward the front of the car but not in this case. Troubleshooting begins with checking to see that there is 12 V supply voltage and ground at the sensor plug, then using a Tech II to observe what is happening with the engine running. If the plug is tight on the sensor and you can see 12 Volts on the RED wire (with the clip up, the right hand terminal) and a good ground on the PNK/BLK wire (center terminal), the sensor is probably bad. Avoid touching the connector terminal for the ORN wire (with the clip up, the left hand terminal) because it goes to the PCM and that circuit is static sensitive.

Connector end view:

2003_CMP_Connector.png

A. ORN, signal to PCM (avoid touching)

B. PNK/BLK, ground

C. RED, 12 Volts power (probably only when the key is on)

This picture is very decieving. The is only about 3" clearance betweem the block and the strut tower. The large wiring harness is overtop of the sensor and a hose is between it and the strut tower. I can barely get my hand in there to even feel it. If I can get the wiring harness out of the way I might be able to get to it. Anyone ever changed theirs on a 2003 Deville?

Edited by PAUL T
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Yeah, the FSM pictures and procedures seem to based on a full tear-down, i.e. with the engine out. On removing the front seal, the 1997 FSM says to "rotate the engine so that the front faces down" which is awkward with the engine in the car. It's tight anywhere on a Northstar. That's why they designed the engine cradle to be moved a couple of inches for a lot of repairs in the car. Try pulling up on the wiring harness and disconnecting the connector first, so that you can pull the wiring harness a bit out of the way.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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That looks like the easiest way to get to it or at least see it. I think I can get to the bolt with the harness out of the way if the heater hose will give a little. Thanks for the picture. I have service manuals for my 92, 94, & 97 Devilles, but nothing above that. My wife is driving a 2004 Deville and my mother-in-law has the 2003. I also noticed that her car has 119,000 miles and I do not know if the plugs have ever been changed. Could that cause the above code too?

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No, old plugs will throw a P0300 but not a P0340 or a lean mixture code. My experience with the platinum plugs is that they are rock solid up to 60,000 miles but anything over that, if you are in a position to get the ones on the rear bank out, you should consider new plugs.

You don't have a miss code, so whether you do change the plugs is up to you.

Since the plugs on the rear bank are such a bear, don't even *think* about anything short of the OEM platinum plugs because anything less will see you changing them more often.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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I learned a long time ago to go with OEM plugs. I have never changed the ones with the Coil on plugs before. I do remember the rear plugs on my 94 & 97 Deville. The 2003 car was bought used so I do not know if it needs plugs or not. I may pull the front ones and gage by that.

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  • 1 month later...

I replaced the Cam Sensor and it ran like a new car. I had to take off the surge tank to get to it. Then, after my father-in-law drove it some he said the surging is coming back. I will have to run the codes and see what shows up. The saga continues.

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This sounds like a bad connector on the cam sensor, or just possibly a bad wire to the connector. Changing the cam sensor resulted in a good connection, which with engine vibration is re-asserting itself.

CTS-V_LateralGs_6-2018_tiny.jpg
-- Click Here for CaddyInfo page on "How To" Read Your OBD Codes
-- Click Here for my personal page to download my OBD code list as an Excel file, plus other Cadillac data
-- See my CaddyInfo car blogs: 2011 CTS-V, 1997 ETC
Yes, I was Jims_97_ETC before I changed cars.

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