ECU resets when hitting a pot hole 2000 cherokee
04-15-2019, 12:29 PM
#1
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Thread Starter
ECU resets when hitting a pot hole 2000 cherokee
HI everyone. I have an electrical issue with my 2000 cherokee xj sport. When I hit a big pot hole with my passenger front tire my ecu resets (check engine light disappears for a while) radio restarts (please note it is not getting reset to factory settings but just turns on and off). I've checked battery to body ground, engine grounds, engine to body ground, pdc power and grounds on driver side fender near air intake box and everything looks tight. sprayed ecu connectors with wd 40 for electrical contacts but no results. I was wondering if someone had the same issue or maybe can tell me where else should I check. Thank you!
04-15-2019, 02:28 PM
#2
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Join Date: Nov 2017
Location: Groton, MA
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Year: 1995
Model: Cherokee(XJ)
Engine: I6 4.0L
Sounds exactly like a loose battery connection, but if you're certain the cable clamps are in good condition and tight I'd be looking at the wiring and seeing if there's something chaffed or exposed.
04-15-2019, 02:40 PM
#4
CF Veteran
Take apart the ECU and look for broken solder joints.
Example of what to look for:
Going crazy:
https://www.jeepforum.com/forum/f13/...tures-1303589/
Example of what to look for:
Going crazy:
https://www.jeepforum.com/forum/f13/...tures-1303589/
Last edited by Dave51; 04-15-2019 at 02:44 PM.
04-15-2019, 04:28 PM
#6
CF Veteran
@Dave51 I thought it might me ECU. I just wasn't sure it could affect the radio. Do you think it can?
My guess is that other things happen during this event but you haven't noticed them.
As unrelated as the 2 events seem, there is one system where they are - Ignition Off Draw. And within that system the wires are not particularly vulnerable, so IMO the weakest link would be a solder joint.
Admittedly this theory requires a little artistic license, but when you have eliminated all other possibilities, whatever remains, however improbable, must be the solution.
04-16-2019, 10:59 AM
#7
Newbie
Thread Starter
Sure. I'll bet you've checked all the grounds and scrubbed them up a million times already. You seem like a savvy guy so you already reset all the fuses and relays.
My guess is that other things happen during this event but you haven't noticed them.
As unrelated as the 2 events seem, there is one system where they are - Ignition Off Draw. And within that system the wires are not particularly vulnerable, so IMO the weakest link would be a solder joint.
Admittedly this theory requires a little artistic license, but when you have eliminated all other possibilities, whatever remains, however improbable, must be the solution.
My guess is that other things happen during this event but you haven't noticed them.
As unrelated as the 2 events seem, there is one system where they are - Ignition Off Draw. And within that system the wires are not particularly vulnerable, so IMO the weakest link would be a solder joint.
Admittedly this theory requires a little artistic license, but when you have eliminated all other possibilities, whatever remains, however improbable, must be the solution.
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04-16-2019, 01:14 PM
#9
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Thread Starter
04-16-2019, 02:20 PM
#10
CF Veteran
Well almost.
In an effort to get my post count up
In an effort to add additional information, a troubleshooting aid could be turn on the visor vanity lights and the dome light and see if they wink out when this happens.
Fuse 16 is like the switch for this function, but don't just rip it out there's a procedure for that (ignition has to be off)
I cannot find the IOD/ECU connection in the wiring schematics yet, but given the draw of the ECU memory it has to be there somewhere.
Regardless, IMO checking the ECU for cold/broken solder joints would be a good idea, especially if all other avenues turn into dead ends.
In an effort to get my post count up
In an effort to add additional information, a troubleshooting aid could be turn on the visor vanity lights and the dome light and see if they wink out when this happens.
Fuse 16 is like the switch for this function, but don't just rip it out there's a procedure for that (ignition has to be off)
When removing or installing the IOD fuse, it is important that the ignition switch be in the Off position. Failure to place the ignition switch in the Off position can cause the radio display to become scrambled when the IOD fuse is removed and replaced.
Regardless, IMO checking the ECU for cold/broken solder joints would be a good idea, especially if all other avenues turn into dead ends.
Last edited by Dave51; 04-16-2019 at 02:22 PM.
04-16-2019, 02:38 PM
#11
Newbie
Thread Starter
Well almost.
In an effort to get my post count up
In an effort to add additional information, a troubleshooting aid could be turn on the visor vanity lights and the dome light and see if they wink out when this happens.
Fuse 16 is like the switch for this function, but don't just rip it out there's a procedure for that (ignition has to be off)
I cannot find the IOD/ECU connection in the wiring schematics yet, but given the draw of the ECU memory it has to be there somewhere.
Regardless, IMO checking the ECU for cold/broken solder joints would be a good idea, especially if all other avenues turn into dead ends.
In an effort to get my post count up
In an effort to add additional information, a troubleshooting aid could be turn on the visor vanity lights and the dome light and see if they wink out when this happens.
Fuse 16 is like the switch for this function, but don't just rip it out there's a procedure for that (ignition has to be off)
I cannot find the IOD/ECU connection in the wiring schematics yet, but given the draw of the ECU memory it has to be there somewhere.
Regardless, IMO checking the ECU for cold/broken solder joints would be a good idea, especially if all other avenues turn into dead ends.
04-16-2019, 03:29 PM
#12
Newbie
Thread Starter
It goes to c1 connector in junction box and from c4 (not sure what s18 means) to radio and instrument cluster. I will pull out and inspect junction box tomorrow
Last edited by Alexey Chernyuk; 04-16-2019 at 03:50 PM. Reason: typo
04-16-2019, 03:38 PM
#13
CF Veteran
So here's where the artistic license comes in (and I'm trying to read into your description):
After an apparent interruption in power, the ECU and radio reboot. Not go dead, reboot. If the ECU lost power you would have come to a screeching halt (but tell me if you did).
Only the radio and ECU were affected. TTBOMK, the only circuit that that could possibly occur in is IOD.
Other devices on the XJ include door locks, vanity lights under the visors, the underhood engine light.
But I don't think Fuse 16 acts like a switch for all those devices. Rather, the overall control should be by the ECU, hence, search for a broken solder connection there.
Of course, there could be something wrong in the PDC, but if the fuse was bad all the stuff would be off.
And anyway, my thought is if there's a problem with the ECU, start with the ECU.
04-16-2019, 03:58 PM
#14
CF Veteran
A sidebar, in 2002 Chrysler applied for a patent for a system where the ECU takes over the function of Fuse 16:
To facilitate electrical testing of the vehicle during manufacture, the ECU 30responds to certain events by activating the circuit-interrupting device 28. In an exemplar embodiment, an event is receipt of a command from a scan tool 44. The scan tool 44 may communicate with the ECU 30 via a communications port 46such as a radio frequency or hardwire link. In yet another exemplar embodiment, the event responded to by the ECU 30 is the activation of the ignition switch 22. The ignition switch 22 may be actuated with a key 48, or via a remote command.
By responding to such events, the ECU 30 controls power to the IOD load 34 while the IOD fuse 34 remains in the manufacture and shipping position 40. This eliminates the need to remove and store the IOD fuse 38 during the manufacturing process.
By responding to such events, the ECU 30 controls power to the IOD load 34 while the IOD fuse 34 remains in the manufacture and shipping position 40. This eliminates the need to remove and store the IOD fuse 38 during the manufacturing process.
Interesting or what?
04-16-2019, 04:10 PM
#15
Newbie
Thread Starter
So although FSM says the PCM is on the IOD circuit, where is it in the schematic?
A sidebar, in 2002 Chrysler applied for a patent for a system where the ECU takes over the function of Fuse 16:
https://patents.google.com/patent/US6759760B2/en
Interesting or what?
A sidebar, in 2002 Chrysler applied for a patent for a system where the ECU takes over the function of Fuse 16:
https://patents.google.com/patent/US6759760B2/en
Interesting or what?