Not another Throttle Body thread!

Robbabob

Original poster
Member
Dec 10, 2012
1,096
Not really... since the battery was changed on the '03 just before purchase, the OBD cycle hasn't completed. In fact, it has run rough a few times while idling (driving slow).

Easy assumption: the pcm is learning the air flow and and the truck no doubt has a dirty Throttle Body. ~getting closer to the reason for the thread~

Since this is a great forum, the FAQ page not only has written instructions w/ pictures, there'a also a video!!!! ~almost there~

Glanced over the instructions.. then watched the video. ~we've made it now~

The video specifically leaves the battery connected, to keep the clock and radio presets, during the entire procedure. He then resets the pcm by pulling the fuses. While the written description says to disconnect the battery.

Is it just a matter of opinion or is there a real reason to disconnect? I am a definite proponent of disconnecting, btw.

Thanks!
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
It's recommended to disconnect the battery for;
1) Safety
2) Reset the PCM
and
3) To prevent having the key in the On/Run position and trying to move the throttle plate. This would/could over power the TP motor (Servo?) and damage the t-body.

It's been a while, but IIRC, the clock needs to be reset, but the pre-sets didn't change.
If you disconnect the battery ( and Roadie will jump in here) make sure you turn OFF all accessories ( HVAC, radio) first.
 

Robbabob

Original poster
Member
Dec 10, 2012
1,096
Wooluf1952 said:
It's been a while, but IIRC, the clock needs to be reset, but the pre-sets didn't change.
If you disconnect the battery ( and Roadie will jump in here) make sure you turn OFF all accessories ( HVAC, radio) first.

I do remember someone stating to turn off everything before disconnecting. Seems odd since, with the key off, nothing is getting power, but I'll do that and possibly need a new master fuse in the morning. ~I must go look for the FAQ for "must parts to keep on hand" in the truck at all times~

Thanks!
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
Turning the HVAC Off, parks the mode doors, just in case the PCM forgets and tries to force them through a reset when you reconnect the battery.
 

Robbabob

Original poster
Member
Dec 10, 2012
1,096
Wooluf1952 said:
Turning the HVAC Off, parks the mode doors, just in case the PCM forgets and tries to force them through a reset when you reconnect the battery.

:cool:
 

MAY03LT

Member
Nov 18, 2011
3,420
Delmarva
Robbabob said:
Is it just a matter of opinion or is there a real reason to disconnect? I am a definite proponent of disconnecting, btw.

It's a matter of opinion. I go more in depth on that subject in the video response that is posted on the throttle video page. There may be some coarse language.

I formed my opinion after working on or reading countless cases in almost 6 years on the forums. The roadie has been doing it longer and has the exact opposite view. The best thing to do is read up on what both sides say, and make your choice from there.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
My opinion is different just because I'm a crankier hardware designer :lipsrsealed: and because I'm a harsh critic of weak components like HVAC actuators :hissyfit: and I don't care how annoying they are to change. If they're marginal, and the recalibration process pushes them over the edge into death, then they deserved it. :wink: Tough love on the actuators.

Like dash stepper motors. Mine have been relatively FINE for eight years, and I thought they might last forever despite being in the bad date code, but one showed an increase in unreliability last month that offended me. So I ordered a set of six, and they ALL have to be euthanized because one of their litter-mates coughed. :mad:

That said, I'm totally sympathetic to the school of thought that says if you can coddle them along and not trigger a recalibration before you have a discharged battery on a cold night a long way from home, you might as well not stress them unnecessarily.

I see a small benefit to taking the risk of having them fail when you already have the vehicle in a place for doing maintenance, and the tools. As always, everybody weighs these things differently. A non-DIYer who was scared about a total dash disassembly would feel differently than me, who has no compunctions.

In my eyes, it's the same thought process that guys (never women, it seems) have when they have a piece of rug crud that the vacuum failed to pick up. We dislodge it from the rug, PICK IT UP for close visual examination, then PUT IT BACK on the rug like a golf ball on the putting green that had been removed as an obstacle to another player, because its fate was to be picked up by the vacuum! This fate was not meant to be thwarted.

On the technical details - I don't always correct every mistaken post, but in my understanding, the short-term memory in the HVAC controller is what gets lost whenever IT (not the PCM or BCM) loses power. The PCM and BCM can't trigger a fresh recalibration when THEY lose power. And the end-point response of the 5 (or 7 - EXT) actuators (the relationship between the CW and CCW commands and the feedback by the position potentiometers) is what's stored in that volatile memory. An odd design choice, but I can see why they made it. I don't recall hearing the "door parking" explanation of turning the system off, but that's easy to check and now I'll be compelled to go do that this weekend. Sigh...I think they just freeze in place, but I may be wrong.

I've seen posters who claim that they haven't killed an actuator yet when they turn the HVAC system off. I can't explain that observation except maybe their actuators wouldn't have failed the other way either. It's a crap-shoot. There's no technical reason that should change anything, because the recalibration is still going to happen anyway and the volatile memory locations are still going to be emptied by the power interruption. It's the unavoidable nature of the hardware they designed the module with.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
Wooluf1952 said:
If you disconnect the battery ( and Roadie will jump in here) make sure you turn OFF all accessories ( HVAC, radio) first.

See? :rotfl:
 

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