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2004 DTS
Joined
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34 Posts
Discussion Starter · #1 ·
Hi,
I have this 2004 Deville DTS and the Cruise Control stopped working when I changed some intake manifold plenum.
I thought I forgot to connect something but couldn't find anything and a friend's scanner gave me code 502 which means some Transmission Speed Sensor is low.
Looking at Rock Auto there are two: Output sensor and Input sensor.
Neither is expensive but I'd like to buy just the right one, so can anybody tell me which is the one?
Incidentally, the car still shows the correct speed while driving so it can't be whichever the speedometer relies on.
Thank you.
PS: is that something a newbie with most tools and some ability can replace? Instructions (foolproof :) ) anywhere?
 

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Administrator
2002 F55 STS, 2014 Explorer XLT, F-150s
Joined
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74,568 Posts
For the Cruise Control check the switches at the top of the brake pedal arm as well as the cables at the throttlebody and Cruise module next to it. The brake pedal switches snap into self-aligning brackets.

To replace the ISS (Input Speed Sensor) inside the transmission REQUIRES complete transmission removal and disassembly. GM shop time is 21.5 hours. Typical cost is about $4200. The ISS is inside the drive chain loop.

No such tihng as a "code 502". Maybe P 0502 - the VSS (Vehicle Speed Sensor) - on top of the right output shaft housing, about where a passenger's left toes would point.


Line art Text Auto part Font Vehicle
Line art Text Line Font Auto part
 

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2004 DTS
Joined
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34 Posts
Discussion Starter · #3 ·
Thank you Submariner409,
Yes, P0502. I thought that's implied. Sorry if not.
It's not clear to me yet which of the two sensors has something to do with the Cruise control or which with the speedometer (so I can eliminate it) although if I'm lucky I don't need the ISS :) .
So can the VSS be the cause of Cruise Control not working? Or is it the one that the speedometer uses in which case it's not what I need?
Thanks again.
And thank you for the drawings.
 

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Super Moderator
2003 Deville Base
Joined
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6,265 Posts
Thank you Submariner409,
Yes, P0502. I thought that's implied. Sorry if not.
It's not clear to me yet which of the two sensors has something to do with the Cruise control or which with the speedometer (so I can eliminate it) although if I'm lucky I don't need the ISS :) .
So can the VSS be the cause of Cruise Control not working? Or is it the one that the speedometer uses in which case it's not what I need?
Thanks again.
And thank you for the drawings.
I assume you know that your car has a built in scanner that is specific to that car and options.
 

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2004 DTS
Joined
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34 Posts
I did check the switches and cables, thank you. I read all the things that I found about things to check.
I'm not saying I didn't miss anything, but I think I covered most obvious things.

Thank you Byrdman,
I do remember having used it once and it felt rather cryptic; that's why I went to somebody with a proper scanner and more knowledge than me.
But even he is unsure which speed sensor is my problem.
I might try the built-in scanner again as it was long ago I last used it and I might remember wrongly.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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21,274 Posts
Thank you Byrdman,
I do remember having used it once and it felt rather cryptic; that's why I went to somebody with a proper scanner and more knowledge than me.
But even he is unsure which speed sensor is my problem.
I might try the built-in scanner again as it was long ago I last used it and I might remember wrongly.
============================

STEP #1 - ALWAYS - check for DTC's - Diagnostic Trouble Codes - using the on-board scanner -
if you don't know how - go here -

post any codes you have -
ALONG WITH THEIR DEFINITIONS -

include whether they are C-Current or H-History -

for code definitions - go here -

here is a how-to video -

=============================
humor us -
use the on-board scanner -
 

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2004 DTS
Joined
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34 Posts
Discussion Starter · #8 ·
Here are the codes I got; all history:
IPC U1016 H; Loss of () Communications with PCM, vcm
RFA U1000 H; Class 2 Communication Malfunction
RFA U1305 H; Class 2 Data Link Low or High
RSS C0615 H, Left Front Position Sensor Malfunction

I initially thought the "U" is a "V" but since there are no V codes...
Also, I know about, and hopefully fixed the last one.

Thanks
 

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2004 DTS
Joined
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34 Posts
Discussion Starter · #9 ·
So nobody can tell me which (if any) of the speed sensors would make my cruise control NOT work while the speed is correctly displayed on the speedometer?
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
Joined
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21,274 Posts
So nobody can tell me which (if any) of the speed sensors would make my cruise control NOT work while the speed is correctly displayed on the speedometer?
====================
the speed sensors ARE monitored -
when/if they fail - a DTC WILL be set -

no speed sensor codes = no speed sensor faults -

you're probably going to need the FSM and a TECH2 scan tool to track down the problem -
 

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2004 DTS
Joined
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34 Posts
Discussion Starter · #11 · (Edited)
A pro with a proper scan tool (can't tell what kind but a serious one) said P0502 was the only relevant code.
He told me a TECH2 would be better but he doesn't have one.
Dealer wants $202/hour to diagnose and I don't think they work in 10 minutes increments :-(
 

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2004 DTS
Joined
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34 Posts
Discussion Starter · #12 ·
So I got it read with a Tech2 scanner and this is what I got about the Cruise control:
588935

I suspect the "Inhibit Signal C" might be the problem but can't find anything helpful on the net?
Does anybody here know about this or what else might cause the Cruise not to work?
Thanks.
 

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Super Moderator
2010 DTS
Joined
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88,463 Posts
I may be wrong, but what I am getting out of that is the TCC/Cruise Brake Pedal switch is bad or misadjusted.
 

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Administrator
2002 F55 STS, 2014 Explorer XLT, F-150s
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74,568 Posts
Cruise will not work (latch ON) until vehicle speed is over 25 or 30 mph. Anything less than that sets the Inhibit function IF the Cruise function switch is ON.

Unless you are on the open road and intend to use long-term Cruise, turn it OFF.

Physically check the brake pedal switches. They're supposed to be "self-adjusting" when correctly snapped into their retainer brackets.

Cruise Control use is discussed in the Owner's Manual.
 

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2004 DTS
Joined
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34 Posts
Discussion Starter · #16 ·
Physically check the brake pedal switches. They're supposed to be "self-adjusting" when correctly snapped into their retainer brackets.
Doesn't the fact that the brake lights come on when I push the pedal mean that the break pedal switches are fine?
 

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Administrator
2002 F55 STS, 2014 Explorer XLT, F-150s
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74,568 Posts
Not necessarily. Cruise should drop out if you barely touch the brake pedal - maybe before the brake lights even come on. If Cruise drops out at a brake pedal touch you use the RESUME rocker to go back to the previously set speed.

I notice that the P 0502 has disappeared so that rules out the VSS, but yes, VSS faults will affect Cruise operation.
 

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2004 DTS
Joined
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34 Posts
Discussion Starter · #18 ·
Not necessarily. Cruise should drop out if you barely touch the brake pedal - maybe before the brake lights even come on.
I think the lights are also supposed to turn on if you "barely touch the brake pedal".
Otherwise it would mean there are two break pedal switches: one for cruise, one for the lights?
 

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Administrator
2002 F55 STS, 2014 Explorer XLT, F-150s
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74,568 Posts
Some vehicles have two switches on the brake pedal arm.

See Posts #2 and #15 - switches.

Cruise does not operate on the open road at speeds over 25 mph ???
 

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2004 DTS
Joined
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34 Posts
Discussion Starter · #20 ·
So I should have tried this as soon as I got the scanner to work yesterday, sorry for wasting your time about the pedal.
Anyway, today I checked that the scanner shows when I activate the break pedal in the Cruise Control display (scanning while I push the pedal show immediate change on/off).
BUT it shows the switches always ON, regardless if I push them or not. Even though the LED status changes on the main switch, the scanner always shows it ON.
So that looks like a bad common ground but where can I look for it? These switches are on the steering wheel.
 
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