Just got back from an uneventfull trip to Myrtle Beach. Any time we make it there and back without breaking down, its a good trip.Had a weird issue on the way there. On I 79 in W VA, when I would hit on of the large expansion joints that are so bad, they make your teeth chatter, the service engine soon light would come on, the headlights would flash, and the tranny would kick out of gear for a split second.It did it 2 or 3 times before i figured out what it was doing. Then it did it a few more times before I stopped for the night.The next morning, it only did it once the rest of the way there.On my way home, it did it one more time.I have NO CLUE where to start troubleshooting because the only way to duplicate the problem is to drive on the highway at about 60 and hit a bad bump.It's a 94 Winnebago on a Chevy chassis with the 454 engine. We caught rain on the way there and it also rained hard the night before we left to come home. I'm thinking its an electrical short caused by moisture somewhere.......exactly where is going to be the stumper.Since its a 94, whould it even have an OBD port to hook a scanner up to? Thanks in advance for your suggestions.

Start with the chassis grounds..it sounds like the bumps make it momentarily lose ground when the connection gets battered.

My 1995 P30 chassis had an OBD I (not II) under the dash just to the left of the steering column. There are still some scanners out there that will read OBD I - some will read I and II.

bullydogs1 wrote:Start with the chassis grounds..it sounds like the bumps make it momentarily lose ground when the connection gets battered.x2. Check the battery connections. Also check the resistance in the ground wires. I've had them corrode between the cable and connector and it was hidden. The only way to tell was by checking the cable resistance from connector to connector. Check the alternator connector to make sure it's securely clipped in place.Check the plug on the ECU to make sure it's not loose. Some vehicles have an issue with the plastic locks on the ECU connector breaking off and it allows the ECU connector to loosen up. The fact that several systems are effected means that it's probably a bad ground or loose wire.

Trouble shooting electrical gremlins are a real pain. I would start with the ignition switch and wiring under the dash. Since you mentioned the headlights, I'm assuming you were driving during darkness or you wouldn't have known they went out. If that's the case, start there and do this at night. Turn the headlights on and wiggle the wiring under the dash. If the lights go out, you can start tracing the wiring and locate your bad ground. If that doesn't work, go the the console where your shift pad is and work there. There is a speed sensor module on the tranny that sometimes gets dirty or loose that also gives your symptoms. Best of luck...unfortunately there's no simple 'look here' solution to your problem. It's simply a matter of tracing it down or waiting for it to break completely, then you meet Mr. Murphy.....Dennis

bullydogs1 wrote:Start with the chassis grounds..it sounds like the bumps make it momentarily lose ground when the connection gets battered.Thats what I was thinking. It does it as soon as the front wheels hit and only if its a really bad bone jarring one. The expansion joints that are angled so that one wheel hits before the other doesn't seem to do it.Would I be looking for a ground strap connected to the frame somewhere in the front?Thanks!

Shorting out | Good Sam Community

bullydogs1
Explorer
Jun 22, 2015
Start with the chassis grounds..it sounds like the bumps make it momentarily lose ground when the connection gets battered.
Clay_L
Explorer
Jun 22, 2015
My 1995 P30 chassis had an OBD I (not II) under the dash just to the left of the steering column. There are still some scanners out there that will read OBD I - some will read I and II.
mabynack
Explorer II
Jun 22, 2015
bullydogs1 wrote:
Start with the chassis grounds..it sounds like the bumps make it momentarily lose ground when the connection gets battered.

x2.

Check the battery connections. Also check the resistance in the ground wires. I've had them corrode between the cable and connector and it was hidden. The only way to tell was by checking the cable resistance from connector to connector.

Check the alternator connector to make sure it's securely clipped in place.

Check the plug on the ECU to make sure it's not loose. Some vehicles have an issue with the plastic locks on the ECU connector breaking off and it allows the ECU connector to loosen up.

The fact that several systems are effected means that it's probably a bad ground or loose wire.
Executive45
Explorer III
Jun 22, 2015
Trouble shooting electrical gremlins are a real pain. I would start with the ignition switch and wiring under the dash. Since you mentioned the headlights, I'm assuming you were driving during darkness or you wouldn't have known they went out. If that's the case, start there and do this at night. Turn the headlights on and wiggle the wiring under the dash. If the lights go out, you can start tracing the wiring and locate your bad ground. If that doesn't work, go the the console where your shift pad is and work there. There is a speed sensor module on the tranny that sometimes gets dirty or loose that also gives your symptoms. Best of luck...unfortunately there's no simple 'look here' solution to your problem. It's simply a matter of tracing it down or waiting for it to break completely, then you meet Mr. Murphy.....Dennis
fuzzbutt
Explorer
Jun 22, 2015
bullydogs1 wrote:
Start with the chassis grounds..it sounds like the bumps make it momentarily lose ground when the connection gets battered.

Thats what I was thinking. It does it as soon as the front wheels hit and only if its a really bad bone jarring one. The expansion joints that are angled so that one wheel hits before the other doesn't seem to do it.

Would I be looking for a ground strap connected to the frame somewhere in the front?

Thanks!
falconbrother
Explorer II
Jun 22, 2015
You might ought to check connectors. Pull them apart, give it a good look, clean them up a bit and use dielectric grease on them. On my old Harleys (both) I had an issue that I chased down to a connector.
Born_To_Travel
Explorer
Jun 22, 2015
The nice thing about the OBD 1 is all you need to pull the codes is a paper clip... http://www.chevytalk.org/fusionbb/showtopic.php?tid/273660
tropical36
Explorer
Jun 22, 2015
fuzzbutt wrote:
Just got back from an uneventfull trip to Myrtle Beach. Any time we make it there and back without breaking down, its a good trip.

Had a weird issue on the way there. On I 79 in W VA, when I would hit on of the large expansion joints that are so bad, they make your teeth chatter, the service engine soon light would come on, the headlights would flash, and the tranny would kick out of gear for a split second.

It did it 2 or 3 times before i figured out what it was doing. Then it did it a few more times before I stopped for the night.

The next morning, it only did it once the rest of the way there.

On my way home, it did it one more time.

I have NO CLUE where to start troubleshooting because the only way to duplicate the problem is to drive on the highway at about 60 and hit a bad bump.

It's a 94 Winnebago on a Chevy chassis with the 454 engine. We caught rain on the way there and it also rained hard the night before we left to come home. I'm thinking its an electrical short caused by moisture somewhere.......exactly where is going to be the stumper.

Since its a 94, whould it even have an OBD port to hook a scanner up to?

Thanks in advance for your suggestions.

Just a shot in the dark here and most likely an intermittent open and whether for grounding or other, so forget the catch all word...short...for describing all electrical malfunctions. Shorts usually blow fuses, too.
Anyway remove the shroud on your steering column just below the dash and you should see some connectors and especially on the left side where you should find a long flat one. Unplug and re-plug every one you can find a few times and wiping a little silicon grease or even Vaseline on the contacts.
Whether it fixes your problem or not, it certainly won't hurt and could prevent some future issues, as well.
fuzzbutt
Explorer
Jun 24, 2015
All good advice. I will make a checklist from all these and work on it this weekend.

Thanks!!!
Krusty
Nomad II
Jun 24, 2015
May not be a short, but likely could be a loose connection, or corrosion in a connector. Your best bet is to find a wiring diagram, and try to determine what all the affected components or systems have in common. ie: Doubtful it would be an ignition switch, as headlamps are powered all the time.

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