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Old 04-30-2010, 10:11 PM   #1
jarl
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Question Gear selector error and other ECU mysteries

I'm in the process of checking lots of things on my '94 TS to buy some peace of mind for a trip in the following weeks (which is why I asked about the ride height sensor... come on! No answers? ).

Today I decided to spend some time checking the codes on the ECU, and logging a few short drives to see what was going on. So... here's what I found:

- The gear selector switch seems to be bad (sometimes seems to oscillate between gears, according to the scanner). There was also a code on the ECU for this. The needle on the dashboard is not aligned correctly with the letters underneath. May this be the problem?

- The car had an unstable idle, and sometimes died when left in park or neutral. AND the dashboard vents were not working from the day we bought it last year. I discovered today that whoever messed up with the engine before me had switched two vacuum hoses: the one coming out of the evaporator canister purge switch was going to the A/C vents, and the one that should have gone to the A/C vents was going to the canister . Switched them and now I have working vents and a stable idle speed. BUT... now I can feel some "pulling" while driving (in Toyota terms, "longitudinal oscillations"). May the ECU be messed up by running with the hoses switched, or is there anything that may have been damaged?

- This is the best one: at some point in time (while checking the vacuum) the car started running like crap. Lo and behold, when I checked the log file of the scanner, looks like the whole car is shutting down at a very fast pace. That is: the battery voltage -and all the other gauges for that matter- go to zero (or very close to it) for a fraction of a second and then back to a normal reading . The car doesn't die, but this can't be normal. Any guesses about what can be the problem?

- The speedometer is reading more than the actual speed (I had confirmed this using a GPS). By checking the ALDL logs, I confirmed the ECU is receiving the right speed measurement, and the problem seems to be the speedometer itself. Is there something that can be adjusted on the speedometer, or is there something specific that I should check?

It's amazing how much information can you get by using some cheap scanner software/hardware, isn't it? Now... if I could only find an easy solution to the problems I discovered...

Any help?
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Old 05-01-2010, 02:38 AM   #2
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Re: Gear selector error and other ECU mysteries

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Originally Posted by jarl View Post
.. The needle on the dashboard is not aligned correctly with the letters underneath....
...I can feel some "pulling" while driving (in Toyota terms, "longitudinal oscillations
Needle position depends on a string attached by a clip to the speed lever at the column....no relation with transmission performance.
..longitudinal oscillations are most probably due to EGR acting...sometimes the computer hesitates between positions and the actual EGR valve hesitation can depend on the position feedback resistor (as 94 has the linear EGR valve). WIth my 93 3 valve EGR, I can feel the hesitation from one combinaison of valves to another....All that is "idiosyncrasy" and without consequence unless aggavated by component failure and then it pops a code.
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Old 05-01-2010, 10:56 AM   #3
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Re: Gear selector error and other ECU mysteries

As always, thanks for the prompt reply

The question regarding the shifter could have been expanded a bit more: it looks like the position of the shift lever on the steering column is determined not by the transaxle, but by stops inside the steering column. Is this correct? If so, is it possible that the cable that goes from the shift lever to the gearbox is not aligned/tensioned/routed correctly?

The oscillations being induced by the EGR make sense... I just hope it's not gearbox-related I guess I'll have to shut the EGR close using a soda can gasket to test that...

I'll see what else can I find in the car...

JR
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Old 05-01-2010, 01:29 PM   #4
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Re: Gear selector error and other ECU mysteries

jarl,

I understand what you are talking about... The column pin for the shift indicator is simply out of line... Its merely a string with a pointer that can be adjusted...

as for the issues you are seeing on the tool with the with the van being in and out of park for no reason has more to do with a bad Park Neutral safety Switch on top of the transmission... The PCM uses this to determine if you have selected Park/ Neutral or Drive.... The starter circuit also passes through the switch...

As for the stalling in the driveway will it restart right away? also did you by chance have a Code 361 or 1361? I think you are having a PCM issue but would like to know if you have the above codes...
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Old 05-01-2010, 10:43 PM   #5
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Re: Gear selector error and other ECU mysteries

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jarl,

I understand what you are talking about... The column pin for the shift indicator is simply out of line... Its merely a string with a pointer that can be adjusted...

as for the issues you are seeing on the tool with the with the van being in and out of park for no reason has more to do with a bad Park Neutral safety Switch on top of the transmission... The PCM uses this to determine if you have selected Park/ Neutral or Drive.... The starter circuit also passes through the switch...

As for the stalling in the driveway will it restart right away? also did you by chance have a Code 361 or 1361? I think you are having a PCM issue but would like to know if you have the above codes...
Thank you JRS,

I'm was just wondering what's going on with the Park/Neutral switch. The car doesn't actually go in and out of park: when you start in park and move the shifter lever through the whole range, the program shows the output of the switch: P->R->N->4->3->2... and then "invalid". If you then go back to 2nd, it will show an invalid output as well. The other positions look ok. So I was thinking that if the position of the gear selector lever is not correctly set in relation to the gearbox, it may happen that the switch ends up in a position that is not really what it should. I.e. it's somewhere in between 1st and 2nd when the lever is in the "1st" position. Does it make sense?

The thing about the car "dying": It happens at idle, and I guess some of the pulling I feel when driving can be the same problem, but no codes are popping up. The OBD log shows the voltage dropping several times (see attachment), although the engine keeps turning. I guess the engine is actually dying for a fraction of a second at a time, but the inertia turns it on again almost immediately. But since I have no codes (yuhuu ) I have no cue about what the problem might be.

The only codes I had where about a bad PRNL switch and bad QDM1 and QDM4. I solved something today by replacing a fuse (15 amps @ convenience center) but I still need to re-scan the car. All I know is that the CEL is off

PD: I just saw something I haven't realized before: the spark advance during the log was at 0BTDC all the time right until the moment it starts running really rough (last few seconds), and then jumps to 40BTDC...
Attached Images
File Type: png OBD scan.png (1.2 KB, 6 views)
File Type: png OBD scan2.png (634 Bytes, 5 views)
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Last edited by jarl; 05-01-2010 at 10:53 PM. Reason: Discovered something...
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Old 05-02-2010, 07:33 AM   #6
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Re: Gear selector error and other ECU mysteries

You are in a tough place and this can leave you chasing your tail..

Find out what is on the Quad Driver circuits, could be a small issue someplace..

I do think you are on the right track with the Park Safety switch... But does the van always restart after a stall? say you started the van cold would it suddenly just shut off after a few minutes? and if it did that would it restart?

Also when it acts like it falls off while driving do all of the gauges drop with the exception of the speedo?
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