P 0741 possible workaround? 00-05 Deville
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, P 0741 possible workaround? 00-05 Deville in Past Cadillac Vehicle Discussion; This is a long-shot... While looking thru the left tail light schematics for the 00-05 Deville I noticed a RIM ...
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    00 Deville's Avatar
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    P 0741 possible workaround? 00-05 Deville

    This is a long-shot...

    While looking thru the left tail light schematics for the 00-05 Deville I noticed a RIM input from the left tail light. On the 00 schematics they call this input "trailer detect" on the 01 and later the same input is called "transmission shift inhibit signal". After reviewing several schematics for Deville's with and without RPO code V92 (trailer towing package) it seems like this RIM input may be to inhibit TCC lockup when either the brakes are applied or the car senses a trailer is being towed for those with the V92 option.

    If my theory is correct could this possibly inhibit TCC lockup and a P0741 code if this input where grounded all the time? Keep in mind this is just a theory at this time. Fortunately I'm not experiencing any P0741 issues at this time (knock on wood). Maybe someone that is... would like to apply a temporary ground to the wire coming out of pin E of the left tail light and report back on the effects on both TCC lockup and P0741.

    Below is the left tail light schematic from an 04 Deville w/o V92.... thoughts?


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    Submariner409's Avatar
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    Re: P0741 possible workaround? 00-05 Deville

    [QUOTE=00 Deville;2708617]After reviewing several schematics for Deville's with and without RPO code V92 (trailer towing package) it seems like this RIM input may be to inhibit TCC lockup when either the brakes are applied or the car senses a trailer is being towed for those with the V92 option. [QUOTE]

    This is why one test for TCC lockup involves touching the brake pedal while holding a steady road speed above 45 mph. In some models the defeat is incorporated in the stop lamp switch circuitry.

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    Re: P0741 possible workaround? 00-05 Deville

    Quote Originally Posted by submariner409 View Post
    This is why one test for TCC lockup involves touching the brake pedal while holding a steady road speed above 45 mph.
    My thoughts exactly.... cars equipped with trailer tow package V92 have a low or ground applied to the RIM defeating TCC lockup when a 5 pin trailer harness is connected to the car. Applying this same ground should have the same effect, tricking the RIM into thinking a trailer is being pulled or brake pedal is being applied... defeating TCC lockup and possibly inhibiting P0741 in theory. But, only a real world test will tell us if this may work.

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    JimD is offline Cadillac Owners Connoisseur
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    Re: P0741 possible workaround? 00-05 Deville

    Quote Originally Posted by 00 Deville View Post
    ....it seems like this RIM input may be to inhibit TCC lockup when either the brakes are applied or the car senses a trailer is being towed for those with the V92 option.
    Think you could find a RIM to PCM connection that might provide a clue or two?

    Personally I would do any trailer towing with the gear selector in 3.

    Good catch, Marty.

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    Re: P0741 possible workaround? 00-05 Deville

    Quote Originally Posted by JimD View Post
    Think you could find a RIM to PCM connection that might provide a clue or two?
    The only connection I was able to find in the FSM was the RIM and PCM talk to each other over the class 2 serial data bus. Too bad they don't show the schematics for the internals of the PCM and RIM so we could tell what type of data is exchanged between the 2 modules.

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    Re: P0741 possible workaround? 00-05 Deville

    Quote Originally Posted by 00 Deville View Post
    The only connection I was able to find in the FSM was the RIM and PCM talk to each other over the class 2 serial data bus. Too bad they don't show the schematics for the internals of the PCM and RIM so we could tell what type of data is exchanged between the 2 modules.
    Making internal schematics available would be giving away their engineering work product.

    The data type is likely little more than a logic 1 (+5 Volts) or a logic 0 (chassis ground). And possibly an interlock loop to confirm all the modules/components are connected.

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    Re: P0741 possible workaround? 00-05 Deville

    yeah, great find marty... so who's going to be the guinea pig?
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    Re: P0741 possible workaround? 00-05 Deville

    Quote Originally Posted by JimD View Post
    Making internal schematics available would be giving away their engineering work product.

    The data type is likely little more than a logic 1 (+5 Volts) or a logic 0 (chassis ground). And possibly an interlock loop to confirm all the modules/components are connected.
    I agree.... it would definitely be binary communication. But this does have me wanting to know more about the data being exchanged. Just going by the name the engineers gave the ground input signal to the RIM ("trailer detect" and "transmission shift inhibit") has me thinking we could be onto something.

    Quote Originally Posted by RippyPartsDept View Post
    yeah, great find marty... so who's going to be the guinea pig?
    I guess the ideal candidate for testing would be a person that has a P0741 on a 00-05 Deville and is comfortable doing a little wiring change on the left tail light... any takers?

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    Re: P0741 possible workaround? 00-05 Deville

    Right now I have 2 2001's with both the 741 and 1860 code. We're in the middle of a monsoon now in the Northeast, but I may try it tomorrow after work.

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    Re: P0741 possible workaround? 00-05 Deville

    That's a great catch 00 Deville! I also noticed that the 2000 schematics does not show the SP402 (splice pack) like the one you posted, it is designated G402. In trying out your theory, a great candidate would also be someone who does have the 0741 code AND who has the v92 (trailer) option. Simply have them hook up the trailer connection and see if the 0741 goes away!

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    Re: P0741 possible workaround? 00-05 Deville

    PA080005.JPGMy 99 has the P0741 without the P1860. Is it the same as the 2000? I have a empty connector on the left side. Would that be the connector to ground and which of the five wires would I ground?PA080004.JPG

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    Re: P0741 possible workaround? 00-05 Deville

    I have P0741 in my 03 Deville and I just passed the emission test by clearing the codes and driving on 3rd for 2 days and then did the test and passed.

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    Re: P0741 possible workaround? 00-05 Deville

    Quote Originally Posted by mjcaddy View Post
    I have P0741 in my 03 Deville and I just passed the emission test by clearing the codes and driving on 3rd for 2 days and then did the test and passed.
    You may have a borderline case of TCC slippage, because per the 02 FSM the test for P0741 runs in 3rd gear, too. In other words, it may slip just enough in 4th (OD) to set the code, but not quite enough in 3rd. Others with P0741 have tried that trick with no joy.

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    Carjockey71 is offline Cadillac Owners Member
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    Re: P0741 possible workaround? 00-05 Deville

    Sign me up, I have both the P1860 AND P1860 trouble codes in my 2003 Deville, I'm game but you need to talk me through it. I have to leave for a day trip to Boston on Tuesday and have to prep for that meeting today and tommorrow, but after that I have a couple days off I could fool around with it, and I DO NOT HAVE A TRAILER hitch.

    I have clear these codes and sometimes (while still in 4th gear) they wont come back fro a day or two, the car has 145K on it. I just got finished putting all new gaskets to from the water pump housing to the block, water pump, thermostat, gaskets, flush, etc. and it seems to be holding together pretty well - (I did have a scare when it went hot y 1st test drive out, but I realize that I had a air pocket on the coolant somewhere so after getting rid of it, it has settled down and is fne)

    Let me know if you guys still want a guinea pig for this!

    Best

    Paul

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    Re: P0741 possible workaround? 00-05 Deville

    Quote Originally Posted by Carjockey71 View Post
    Sign me up, I have both the P1860 AND P1860 trouble codes in my 2003 Deville... I'm game but you need to talk me through it.
    Let me know if you guys still want a guinea pig for this!
    Paul, I'm assuming you you had a code typo above and you have a P0741 and P1860. I can't promise you anything... this is merely an unproven theory. If you would like to give it a try, it should be a fairly simple experiment if you have a few basic electrical skills.

    You will need to gain access to the left rear (drivers side) tail light wiring. Access is gained by removing the 2 black plastic cargo net retainers and a plastic push pin from the left side of the trim piece around the trunk opening. You should then be able to pull back the carpet to expose the wiring. You will be looking for the gray wire that goes into the left tail light connector. You will now need to apply a ground to this gray wire.... there are several ways that you can do this.

    -use a crimp on wire tap to add a section of wire to a suitable ground.

    -strip back the insulation with a razor blade to apply a ground.

    -cut the wire and ground the end that goes to the RIM.

    Don't tap into the wire too close to the electrical connector, you will want to give yourself plenty of wire to make it easier to spice back together if this doesn't work. Make sure that your connections are not loose and you have chosen a good grounding point. Good Luck!!!

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