Weird ECU problems...

ISpy · **Posted:** Mon May 28, 2007 6:26 pm

Here's one for the experts. After start and driving for the first 4 or 5 minutes the speedometer isn't working and the auto door locks don't lock. Then, after around 4 or 5 minutes, I get one single tone and the speedometer starts working and the doors lock. Also, after around 10 minutes another single tone chimes for no reason that I can detect. There is no message or lights with these chimes. Do I have a slow ECU? Any suggestions?

ATXKJ · **Posted:** Mon May 28, 2007 6:59 pm

a slow ECU would operate in the 10-20 mhz range - anything in the minute range is a system problem.
probably needs the dealers computer to talk to your computer - something's wrong.

ISpy · **Posted:** Mon May 28, 2007 7:56 pm

Thanks ATXKJ. Before I waste all day in the stealership do you think I can reset the ECU somehow and see if it fixes it?
To reset ECU on some cars you just have to disconnect the battery for 10 to 15 miutes or so to reset it. Is this the same on the Liberty and what is the process and disconnect time for the quick reset if it is possible? Thanks for the replies.

myjeepwalks · **Posted:** Mon May 28, 2007 9:00 pm

sounds like a bad bcm.

ATXKJ · **Posted:** Tue May 29, 2007 12:56 pm

I don't know if disconnecting the battery will clear anything - some codes are stored in a non-volatile memory so they have to be erased, and some things seem to be reset by unplugging the battery (I've even had the engine reset by turning it off and back on) so you can try the battery and see if it helps
(and hour in the driveway is better than a day at the dealer)
Good luck

ISpy · **Posted:** Wed May 30, 2007 11:31 am

I've had this Jeep for only 3 months but it seemed to start after the rear passenger door lock actuator was changed because it wasn't locking. Maybe the PCM needs to memorize the new part? The auto door lock over 15 mph and speedometer needle is the only thing that seems to not be working until 4 or 5 minutes of driving. It is happening less often now so I'm thinking it has to go through the 50 cycles for PMC memory to acknowledge the new part? I'm thinking of disconnecting the positive battery terminal to clear the PCM memory but waiting to see if it programs on it's own.
A computer check would be good but you know what a hassle and $$$ stealerships can be.

hoku5 · **Posted:** Thu May 31, 2007 12:45 am

This sound like the same problem I had couple of years ago but I had a fault code, I don't remember what it was but ended up to be a speed sensor on the transmission. There are 2 on the left (driver side) side of the transmission. Both of them are the same p/n went to the dealer and bought 2 of them about $45.00 each. Each sensor has 2 wires and 1 bolt easy to change. I decided to change 2 and use the old one for spare. This problem also effected my headlight cause it wouldn't come on.
Sound like you have a weak sensor or bad connection. I would remove the connection from the sensor and clean it first before buying the sensor.
Just before Moab at the super market my door locks wouldn't respond to my remote and my speedometer wasn't working again when I got home cleaned the connection on both sensors and been working since.
I don't have any p/n info but when I get home this weekend l'll get them for you. If I remember the wiring print identify those sensors as speed sensor in and speed sensor out to the ECU. Also the sensor should come with new O-rings on them. Hope all of this info helps.

myjeepwalks · **Posted:** Thu May 31, 2007 1:24 am

ISpy wrote:

I've had this Jeep for only 3 months but it seemed to start after the rear passenger door lock actuator was changed because it wasn't locking. Maybe the PCM needs to memorize the new part? The auto door lock over 15 mph and speedometer needle is the only thing that seems to not be working until 4 or 5 minutes of driving. It is happening less often now so I'm thinking it has to go through the 50 cycles for PMC memory to acknowledge the new part? I'm thinking of disconnecting the positive battery terminal to clear the PCM memory but waiting to see if it programs on it's own.
A computer check would be good but you know what a hassle and $$$ stealerships can be.

Nothing needs to be programed for a door lock actuator, it's the equivilent to replaceing a window motor. It's just plug and play. Check those sensor connections like hoku5 said. It's worth a shot, also disc. the battery for a few minutes. You have something going on and without the diagnostic equipment its tough to pin point.

ISpy · **Posted:** Thu May 31, 2007 3:11 pm

Thanks hoku5, I'll check out and clean those sensor connectors before changing them. It hasn't been acting up for the last 5 or 6 start-ups so I'm kinda waiting to see if something breaks so I can find the fix but that is a good place to start. Thanks again.

Weird ECU problems...

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