Rocket Surgeon!

As stated, I have seen several threads on this... without solid answer.

4 days ago I noticed at the end, last 5 miles, of a 45 minute drive cycle that the transmission was shifting harshly. Most noticeable from a stop to go, or if placed in neutral to drive, harsh engagement. I only observed this on one drive cycle.

Since then I noticed the autolock/ unlock not working, though I did notice and observe twice that only the driver's door (and no others) locked when placed in drive, but did not unlock when placed in park. I suspect this may have occurred randomly a hand full of times in the last weeks.

Last night Cruise control stopped working.

Last night I also noticed shifting to I or L did nothing.

On the way to work just now, I observed I lost torque converter lockup. It may have not worked last night. 70mph is giving me about 2600RPM, and touching the brakes does not increase the RPM as consistent with tcc releasing.

I am not observing the shift interlock clicking when stepping on the brake, but I have never heard it work.
edit: shift interlock clicks in all gears.

Check engine light is not on, it still works when key on... but I have not grabbed my scanner to see if non light codes are present.

Have not verified autostart, I would suspect it is inop.

Engine runs fine, no other electronic have been noticed to be inop/fouled up, such as gauges and radio, etc.



What advice might you ladies and gentiles have? thanks!

UPDATE FOR POSTERITY:
It was a weak battery that measured about 11.5 volts. Probable that the Body Control Module was being under powered leading to functions it was responsible being affected.
TCC lockup may be a separate issue.
Further update:
TCC lockup has returned, but voltage vehicle running is 12.5 volts... alternator is 3 months old.

donbrew

Did you check the CHMSL (center brake light)? Battery & charging system? Shift cable adjustment? Brake light switch?
If the torque converter clutch isn't working there is a code. If any of the solenoids aren't working there are codes.

If you have a 2.4L you might just replace the VVT valves. And take a look at the timing chain.

Rocket Surgeon!

third brake light is working.

I can confirm that the shift interlock clicks even in gear.

remote start does not work as expected.

Have not gotten around to codes check yet, no light set.

Is there any way I can procure a service manual, by chance? All these simultaneous failures have to have something in common.

Thanks.

Rocket Surgeon!

I went and found the response i had from a previous thread. I notice that the BCM controls autolock and unlock. Are all these functions I described above as malfunctioning BCM controlled?

Oldblue

You are describing a failing battery, have your battery load tested , anything less than 12.4 volts is a dead battery.

Also check the under hood fuse box , make sure the bolts are tightened and the fuses and relays are firmly inplace

donbrew

Make sure the maxi-fuse by the battery is seated well and the wires are good. That powers the BCM.
Check the battery and charging system (again)..
Hearing relays click is a sign they are not getting enough juice.
Check you PM.

Rocket Surgeon!

Not a relay clicking, just the shift interlock clicking, It should only operate in park but is clicking in all gears. Basically functions related to the gear shift position are affected, manual downshift, safety interlock, TCC lockup, cruise control... While the transmission is otherwise acting okay as far as gears 1-4, something doesn't know what gear the car is in.

I wonder if this affects the car starting only in park and neutral..... might check that,,,

It's now my day off, I will test battery and check relays. I will try to scan the car for diagnostic codes although the check engine light has not illuminated. Alternator was replaced 3 months ago. Battery is just over 3 years old.

Thanks for the PM!

Thank you!

donbrew

What do you think the shift interlock is? If not relays.
I think your understanding of I and L is incorrect. they don't mean first and second like the 70's, the are ranges and shift point changes. That's why they aren't marked 1 & 2 & 3; it is a 4 speed, after all.
Age of a battery does not make any difference. But, It is hard to find a battery with more than 36 month warranty.
As Oldblue and I have already said "you are describing symptoms of a bad battery". Computers don't like to be underfed. They won't work at all under 9V and don't like under 12.5V.

PulpFriction

Anxiously awaiting the codes.

By all means get the battery tested, but do not believe their analysis. They’ll load test it and that’s nice, but they can't tell you if it’ll hold 12.6V overnight, or a week or two. If it won’t, it might give you trouble. I replaced but saved an OEM battery from my 2011, so now 11-12 years old, that still holds 12.7V for months.

If it’s an older battery, just replace it. It adds all kinds of doubt trying to diagnose electrical problems with an iffy battery. It will be the cheapest part of the solution. Maybe the entire solution.

Rocket Surgeon!

The shift interlock is a solenoid on the shifter that allows you to shift out of park when actuated. There is likely a relay involved, but the click is the solenoid. I had to disable it in my parents 95 ciera long ago as it would bind up and worked very slow... also the next nearest part store or junkyard was at least an ocean away.

Code P1818 present, does not light check engine light.
"The ECUs uses a signal from the transmission fluid pressure manual valve position switch / TFP manual valve position switch to calculate line pressure based on the selected gear ratio. A P1818 DTC means the TFP manual valve switch thinks that Drive is selected, but the ECU sees a different gear."
That seems consistent with I and L not responding the manual downshift

Scanner saw a 11.602 and 11.524 battery voltage.

Can't find one of my eleventy billion multimeters to get a direct battery read yet.

Barring a a poor electrical connection, I believe it is the battery. Especially as GF has flatlined the battery at least once....

Will check and test ASAP. Probably tomorrow.

...and update for posterity's sake.

Thank you for the help!!!!!!