Jump to content
CaddyInfo Cadillac Forum

Big Problems with my Caddy tonight!


Recommended Posts

Ok, after almost a year of no major Caddy issues my car freaked out on me tonight on the freeway to and from work.

I'm pulling these PCM Current Codes:

P0174

P0171

P0503

My digital Speedometer was going wild as well as RPM's. Just had the oil changed yesterday, but I'm assuming that has nothing to do with it running lean. After the problem started today I figured maybe I had wore out the fuel pump or there was condensation in the tank, so I filled the tank and added a bit of that "no freeze" stuff to the mixture. This has to be a bad sensor somewhere - otherwise my speedometer and RPMs wouldn't be jumping around right? The car also seems to hesitate when this happens. Runs pretty well up to 40 MPH, then the freakout begins. Help! I'm not gonna drive her again until I can figure this out.

Link to comment
Share on other sites


You are also getting

P0503 - Vehicle Speed Sensor (VSS) Circuit Intermittent

Your speedometer messing up or blanking out because of the VSS sensor or connector. The VSS is located on top of the Right output shaft of the transmission, check its connection is solid and if it is replace the VSS.

Those two codes P0171 and P0174 reflect a lean condition on both banks. On later models (not yours) its common for the rubber plenum between the intake and throttle body to tear allowing unmetered air into the intake causing a lean condition on both banks.

You need to check for things that cause 1) a reduced FUEL delivery or 2) a vacuum leak that affects both banks

Reduced fuel delivery causes, put a fuel pressure gage on the fuel rail, check pressure and check for

clogged fuel filter

fuel pump output low

kinked lines

check FPR

Check for vacuum leaks

vacuum hose at brake booster

vacuum hose leak

loose intake manifold

leak at intake over pressurization valve (do you hear a whistle)

leaking seal at throttle body to intake (not likely)

cracked intake

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

You stated that the "digital Speedometer was going wild as well as RPM's". Were the RPM's actually fluctuating? Or was the gauge just going nuts? If it were JUST the gauges then a bad relay could be possible.

From what I read elsewhere, a faulty VSS will cause RPM fluctuation and speedometer problems.

I do find it odd you got all these codes at once. Is there anything anyone can think of that could have caused BOTH conditions, or at least tie them together?

big4870885.jpg

Link to comment
Share on other sites

You stated that the "digital Speedometer was going wild as well as RPM's". Were the RPM's actually fluctuating? Or was the gauge just going nuts? If it were JUST the gauges then a bad relay could be possible.

From what I read elsewhere, a faulty VSS will cause RPM fluctuation and speedometer problems.

I do find it odd you got all these codes at once. Is there anything anyone can think of that could have caused BOTH conditions, or at least tie them together?

Yes the RPMs were flucuating, as well as my speedometer. I have no idea where the other codes came from, but it's weird to me as well that they all struck at once

Link to comment
Share on other sites

"Your speedometer messing up or blanking out because of the VSS sensor or connector. The VSS is located on top of the Right output shaft of the transmission, check its connection is solid and if it is replace the VSS."

Great - I need specific instructions on where exactly that is. Not much of a car mechanic, but I'm handy. Thanks!

Link to comment
Share on other sites

P0503 - Vehicle Speed Sensor (VSS) Circuit Intermittent

"Your speedometer messing up or blanking out because of the VSS sensor or connector. The VSS is located on top of the Right output shaft of the transmission, check its connection is solid and if it is replace the VSS".

I need someone to guide me through this step-by-step to locate and check the VSS conection.

Link to comment
Share on other sites

That was pretty detailed but

Here is the location, see the arrow

4T80ElectricalComponents-1.jpg

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

You can see the VSS from behind the right front wheel. It's simpler if you turn the steering all the way to the left before you crawl under the car. It's on top of the half-shaft a few inches from the end of the transmission. It has a connector that pushes down from the top.

One thing that can cause P0503 is excess coolant being expelled from the surge tank. The drain hose from under the radiator cap exits in front of the half-shaft and coolant can wet the VSS. In fact, this was one of the first symptoms I had of my HG problem, but it can also be caused by over-filling the coolant, a common thing to happen when you have your car serviced. If the VSS connector seems damp, wipe it off with a paper towel as best you can from under the car.

The P0171 and P0174 codes can be caused by a bad air filter. If someone put in the wrong one as part of the service, or shook it out to clean it, that might happen. If the service people did replace it, get a new AC/Delco air filter element and replace it yourself.

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.

Link to comment
Share on other sites

We started to give you info on your VSS here, there is no need to start a second thread on that, I merged that thread here, I posted a photo of its location, access it from the top of the output shaft or through the passenger side wheel well.

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

Thanks! I'll give it a shot this afternoon. Sorry to ask for so much detail but I'm not very quick when it comes to things I've never dealt with

No biggie, there is not much to say, just check the connection to make sure its clean and tight, if it is, replace the VSS, its held by one 10mm bolt if I recall

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

Also, I'm just in a rush to get it fixed. Can't miss work tonight - normally I wouldn't start a second thread

Its ok to start one, but we got down the road on this already, and its more efficient to keep it together.

The VCC is the least of your trouble, the lean condition will be the challenge. No doubt the VCC just needs replacing

I will say that it is odd that your speedometer and lean condition started at the same time, where did you get your oil changed?

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

Also, I'm just in a rush to get it fixed. Can't miss work tonight - normally I wouldn't start a second thread

Its ok to start one, but we got down the road on this already, and its more efficient to keep it together.

The VCC is the least of your trouble, the lean condition will be the challenge. No doubt the VCC just needs replacing

I will say that it is odd that your speedometer and lean condition started at the same time, where did you get your oil changed?

Precision Tune Auto Care. I won't be going back there again.. All I can say is that it was running fine BEFORE I took it there.

Link to comment
Share on other sites

It could just be coincidence

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...