Went to get a back up camera installed today and the guy told me that my reverse lights do not have power, and this is what they plug the camera end into.

I am thinking that the power issue is somewhere in the transmission. Tried removing the shifters, however the bolts did not seem to be turning. Can you remove this from inside the cab? Even with it removed will I be able to see the wire to make sure their is a connection?

Thanks, Matt

 

The shifter has 5 wires. Two wires are for the neutral safety switch, two are for the reverse light and one for the shifter LED light. AS I REMEMBER ........ The reverse switch wires are the 2 forward military connectors that have MALE ends. The NSS have two female ends. The LED is a smaller size diameter connector.

I would measure the resistance across the two reverse switch wires while someone moves the shift lever through its paces, engine off. There should be infinite resistance in all positions except when in reverse. At this position, the shifter plate pushes in the small round contact end of the switch, to enable a circuit. Be sure to chock the wheels so you don't get run over.
Gil

 

Hey Gil, welcome to HF.

 

Thanks for the welcome.

I just found that there is a fuse for the "back-up lights". For a 1996 truck, it is 3c. I assume this carries on for other year trucks but the exact fuse position may change.

So if your switch is good, I would check this fuse. If that is also good, Then you need a circuit diagram to determine if one of the wires to the reverse switch is always hot. Most likely this is true. The circuit is probably completed when the shifter presses the bearing ball into the reverse switch when placed in the reverse position.


Gil

 

Thanks Gil for the response, I appreciate you taking the time. If possible could I get some further clarification on some of your points.

"I would measure the resistance across the two reverse switch wires while someone moves the shift lever through its paces, engine off. There should be infinite resistance in all positions except when in reverse. At this position, the shifter plate pushes in the small round contact end of the switch, to enable a circuit. Be sure to chock the wheels so you don't get run over."

-Do you take this measurement from inside the truck or underneath. I do not know the correct place to access these items?

-I am confused on moving the shift lever if their is going to be "infinite resistance". Doesn't that mean the shift lever should not move at all and stay in park?

Thanks,
Matt

 

Beneath the truck, the entire shifter mechanism is covered by an external silver grey heat resistant cloth bag with snaps. This is found near the driver's side frame rail, attached to the truck floor at about the level of the begining of the transmission. If you open this bag up, you will see the 5 wires as well as the shifter levers that are connecting to the rods that go to the transmission and T-case.

Military connectors are black round and cylindrical, designed to be water tight. You pull these apart (with some effort). To reassemble, I like to wet the rubber grommets with Windex so they slide together easier. These connections have a male (cylindrical solid) and female (cup shaped) side.

When you find the two proper connections, using a multimeter, place it into Resistance mode. If the shifter is in any position other than Reverse, the resistance reading should be infinity. It is an open circuit. If you move the shifter into reverse, it should be near 0 ohms. You have a closed circuit through that reverse switch.

However, before I explored this reverse switch, I would find the location of that fuse (3D) for the Backup Light circuit FIRST and make sure it is not burned out (blowing a fuse is common). This fuse is in the fuse panel located beneath the black plastic kick panel, to the left of you knees. There is a little trap door to remove and the min-fuses are covered by two removable rectangular block box covers. A 1997.5 is probably identical to my 1996 for fuse location, but you need to verify that. Be sure to pull the fuse and make sure it is good as are the connections in the fuse panel. Water leaks can cause corrosion of these fuse contacts. Check the fuse continuity (resistance) with a multimeter. Similar procedure as testing the reverse switch in the shifter mechanism. Sometimes fuses look good but are really burned out.

If the fuse is GOOD, replace it then with ignition ON but engine OFF, touch a multimeter probe (set for a DC voltage reading) to the top of that mini-fuse on the right or left side silver button (or push the probe into the left side of the fuse holder with the fuse out). If I remember the circuit correctly, you should see 12 volts. Remember the grounds on a Hummer H1 are wierd so I connect the other side of the multimeter to the grounding block under the left kick panel to guarantee a circuit for this test or run a wire directly to the Negative of the battery. You should see 12 volts. Because I do not remember the details of the circuit, I would also try these steps: If no voltage in the first test, try it with the truck running. If no voltage in both tests, try it with the truck running and place the truck in Reverse. If no voltage in any test, you have a bad circuit.

You should get the AMG CD manual for your year truck. These are available from most Hummer parts resellers. A CD has both a parts manual and a service manual. This way you can look up the parts we are discussing and their locations.
Gil

 

Thanks for taking the time for the thorough reply.

I am sure it is not the fuse, and I have followed the reverse lights from the lights to the transmission and know that there is no power to those lights (both items were professionally checked).

 

I checked the schematics for a 1996. Your backup light has absolutely nothing to do with the transmission other than a reverse switch is located in the shifter mechanism and gets activated when placed in reverse (connecting rod obviously moves thee transmission selector into reverse position at the same time). Your expert mechanic is incorrect.

This circuit is always energized all the way to the reverse switch in the shifter mechanism when the ignition key is in the ON position. When you move the shifter, the reverse switch closes the circuit to complete the circuit.

The shifter reverse switch has an orange wire which is hot (getting power from the L1 buss). When the circuit is complete it sends the electricity through a brown wire directly to both reverse lights in the respective tail light assemblies.

There are only two connections of harnesses involved: C1, the 76 way body harness in the engine compartment. Pin 43 on Circuit 298 having a Brown wire. C2 the 42 way underbody connector on the left foot well near the engine. Pin 13, Circuit 298 with a Brown wire.

Everything I said in previous posts (from the top of my head) is correct including how to troubleshoot the issue. If you do not have power in this circuit then you have several choices, a harness (main body or underbody) has been damaged or either C1 or C2 connectors have a pin issue.

As a test, run a wire from the battery to this reverse switch and see if your reverse lights work when you shift into reverse.

As a permanent solution: Run a new wire from a ignition keyed ON hot source to the shifter reverse switch (orange wire).

If you want the schematics, e-mail me at gilbertherman@comcast.net. The PDF exceeds the file size allowed in the WWW forum.
Gil

 

Found this in my 2001 CD
Gil