Blown fuse when shifting into reverse
- Thread starter WRfarmer
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I'm not experienced at wiring. How do I trace/isolate the problem? Could it be the switch for the back up lights? It Blows the fuse every time I put it in reverse.
HiluxSurf SSR-G
Senior Member
was the back-up switch done recently? the issue could be there. try crawling under the steering column and try to take a look at it
TheDurk
Elite Member
He will look a long time under there. He has a manual. Switch is on the side of the transmission about at the halfway height. I think it's left side but not sure. Easily seen and reached from underneath, unlike the T-case switches. Confirm that wires are red-yellow and black-yellow. Try unplugging the switch, and then bridging the two wires in the plug. If the lights then come on, you have a bad switch. If the fuse blows that way, try disconnecting at each of the rear lights in turn and remove bulbs. If no joy, you are going to have to trace that whole red-yellow wire. I can help with that if necessary.
They do sell cheapo Chinese switches for the manual back-up light so one of those could be the issue. NAPA sells a good Echlin one for a decent price.
Here is the circuit diagram for 2000.
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ElectroBoy
Banned
Looking at the wiring diagram, you have a short to GND either at one of the reverse bulbs or socket, or somewhere along the wiring path. I’d first suspect a problem at the bulb.
Have you replaced your reverse light bulbs recently? Maybe with LEDs? The pins in the socket may have gotten squished together and are shorting the +12 to GND when you go into reverse. Or a bulb actually is a dead short. Some LED bulbs have been known to be failed in a shorted condition.
Turn ignition off. Install a new fuse. Remove the reverse bulbs. Inspect the sockets for shorted pins. Measure the resistance between the bulb’s two pins. It should be low resistance of a few ohms. Reverse the leads and measure again. If you get a zero ohm reading you have a shorted bulb. There’s your culprit. Repeat with the other bulb.
If each bulb is OK measure the resistance of each pin of each socket to chassis GND. Only one pin in each socket should be GND. The other pin should be open. If both pins at one socket are shorted to GND you have a shorted wire to chassis somewhere between the bulb socket and the switch, or the switch itself, that you’ll have to trace. If only one pin is GND, set brake, chock wheels, turn on ignition, put it into reverse. Fuse blows? Suspect a bad reverse switch. Fuse OK? Set your meter to read DC volts and read across the pins at each socket for 12V. Take care not to short them together. If you read 12V, turn off the ignition. Install one bulb. A known good incandescent OEM bulb and turn on the ignition and repeat the reverse test. Bulb lights OK? Turn off ignition. Install other bulb and repeat reverse test. Bulb lights? You’re good to go.
Have you replaced your reverse light bulbs recently? Maybe with LEDs? The pins in the socket may have gotten squished together and are shorting the +12 to GND when you go into reverse. Or a bulb actually is a dead short. Some LED bulbs have been known to be failed in a shorted condition.
Turn ignition off. Install a new fuse. Remove the reverse bulbs. Inspect the sockets for shorted pins. Measure the resistance between the bulb’s two pins. It should be low resistance of a few ohms. Reverse the leads and measure again. If you get a zero ohm reading you have a shorted bulb. There’s your culprit. Repeat with the other bulb.
If each bulb is OK measure the resistance of each pin of each socket to chassis GND. Only one pin in each socket should be GND. The other pin should be open. If both pins at one socket are shorted to GND you have a shorted wire to chassis somewhere between the bulb socket and the switch, or the switch itself, that you’ll have to trace. If only one pin is GND, set brake, chock wheels, turn on ignition, put it into reverse. Fuse blows? Suspect a bad reverse switch. Fuse OK? Set your meter to read DC volts and read across the pins at each socket for 12V. Take care not to short them together. If you read 12V, turn off the ignition. Install one bulb. A known good incandescent OEM bulb and turn on the ignition and repeat the reverse test. Bulb lights OK? Turn off ignition. Install other bulb and repeat reverse test. Bulb lights? You’re good to go.
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Pair of 3rd Gens
New member
98' 4Runner 10A gauge fuse blows when put in reverse - SOLVED
1998 4Runner 4WD, Limited, AUTOMATIC, 5VZ-FE 3.4L V6, 244,400 miles
10A gauge fuse randomly blows when car put in reverse.
Items checked or repaired:
- inspected wiring inside fuse panel - no issues
- checked vehicle grounds for good connections - no issues
- trailer harness wiring checked - no breakage, good harness and connector and good ground
- replaced reverse tail light bulbs with LED - no bad factory bulbs
- checked tail light bulb sockets, harnesses and wiring for corrosion/breakage - no issues
- replaced neutral safety switch on transmission (automatic v6) with new NAPA part- original factory switch was still functional
- traced and inspected wiring bundle and harnesses from tail lights to neutral safety switch on transmission and inside cab - no damage or corrosion
SOLUTION:
Upon inspection of wiring section from transmission up to the junction box, found a section on the engine wiring harness that had no wiring loom protection underneath the intake plenum. Found small area of red/yellow wire had rubbed through the insulation on a valve cover bolt. Wiring section with issue starts at the "Y" junction of the engine wiring bundle right by the oil filler cap and proceeds towards the center of the engine and then turns and goes underneath the intake plenum. Verified 3 times via wiggle test the source of the short had been located. Sealed exposed wiring with liquid sealant and wrapped with new protective loom.
10 hour search for the issue and 15 minute $5 repair.
I searched all the forums and found multiple threads with the exact issue but not one of the threads shared their specific solution to the issue on a 3rd gen v6 AUTOMATIC so I hope this information helps someone else of how my blown 10A gauge fuse issue was solved on 3rd gen automatic.
Cheers,
Pair of 3rd Gens
1998 4Runner 4WD, Limited, AUTOMATIC, 5VZ-FE 3.4L V6, 244,400 miles
10A gauge fuse randomly blows when car put in reverse.
Items checked or repaired:
- inspected wiring inside fuse panel - no issues
- checked vehicle grounds for good connections - no issues
- trailer harness wiring checked - no breakage, good harness and connector and good ground
- replaced reverse tail light bulbs with LED - no bad factory bulbs
- checked tail light bulb sockets, harnesses and wiring for corrosion/breakage - no issues
- replaced neutral safety switch on transmission (automatic v6) with new NAPA part- original factory switch was still functional
- traced and inspected wiring bundle and harnesses from tail lights to neutral safety switch on transmission and inside cab - no damage or corrosion
SOLUTION:
Upon inspection of wiring section from transmission up to the junction box, found a section on the engine wiring harness that had no wiring loom protection underneath the intake plenum. Found small area of red/yellow wire had rubbed through the insulation on a valve cover bolt. Wiring section with issue starts at the "Y" junction of the engine wiring bundle right by the oil filler cap and proceeds towards the center of the engine and then turns and goes underneath the intake plenum. Verified 3 times via wiggle test the source of the short had been located. Sealed exposed wiring with liquid sealant and wrapped with new protective loom.
10 hour search for the issue and 15 minute $5 repair.
I searched all the forums and found multiple threads with the exact issue but not one of the threads shared their specific solution to the issue on a 3rd gen v6 AUTOMATIC so I hope this information helps someone else of how my blown 10A gauge fuse issue was solved on 3rd gen automatic.
Cheers,
Pair of 3rd Gens
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Ch1ckenW4ffles
Junior Member
Hate to revive a dead thread but I’m having this issue and want to try some of the easier solutions first. How do you disconnect it?
My 3rd Gen Automatic is still fairly new to me and I’m still getting used to everything.
You can clean the internal wire pins inside the trailer wiring.. Do this with ignition OFF. IF that does not solve the issue, check the light bulbs inside the tail lights. Unscrew both bolts and then tap the housing to the side of the vehicle to come off the plastic mounts.
