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Lamp-Out Module Testing
 
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Pelican Technical Article:

Lamp-Out Module Testing

Nick Czerula

Time:

2 hours2 hrs

Tab:

$200

Talent:

*****

Tools:

10mm, T25 Torx driver, DVOM, test light

Applicable Models:

Volvo V70 (1998-01)
Volvo V70 2.4T (2001)
Volvo V70 AWD (1998-99)
Volvo V70 GLT (1998-00)
Volvo V70 GLT SE (2000)
Volvo V70 R (1998)
Volvo V70 R AWD (1999-00)
Volvo V70 T5 (1998-01)
Volvo V70 X/C (2001)
Volvo V70 X/C AWD (1998-00)
Volvo V70 X/C AWD SE (2000)

Parts Required:

Lamp out warning module

Hot Tip:

Use an incandescent test light to simulate bulbs

Performance Gain:

Proper working lamp out display

Complementary Modification:

Replace tail light bulbs

The lamp-out warning module is used to notify the driver of a bulb failure in the headlights or taillights. When a light bulb is not recognized by the module a warning light in the instrument cluster is illuminated. The lamp-out warning module receives the battery positive signal from the switch and relays it to the bulb. The bulb is connected to the vehicle's chassis ground. Internal resistors monitor circuit current. When the bulb circuit current is not as expected the warning light is illuminated.

If your bulb warning light is ON, always start by checking your headlights. If the headlights are OK, move to the taillights. Check all the rear lights for proper function. If you still have a warning light, use the steps below to determine which part of the circuit or bulb is causing the issue.

This module can also fail causing the brake lamps to fail. You could have a non-working third brake light or main stop lamps. If you have this issue, check the feed into the module and out to the bulbs. See the testing steps below.

Remember that your car may have been serviced before and had parts replaced with different size fasteners used in the replacement. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches.

Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability.

Our vehicle may vary slightly from yours as models do change and evolve, as they grow older. If something seems different, let us know and share your info to help other users. Do you have questions or want to add to the article? Leave a comment below. When leaving a comment, please leave your vehicle information.

I suggest using a current wiring diagram when testing your vehicle, as the wiring or circuit connectors may vary from my subject vehicle.

The lamp-out warning module is used to notify the driver of a bulb failure in the headlights or taillights.
Figure 1

The lamp-out warning module is used to notify the driver of a bulb failure in the headlights or taillights. When a light bulb is not recognized by the module a warning light (red arrow) in the instrument cluster is illuminated.

Working in the cargo compartment, remove the storage compartment lid by opening it and lifting it (green arrow) out of the mount (red arrow).
Figure 2

Working in the cargo compartment, remove the storage compartment lid by opening it and lifting it (green arrow) out of the mount (red arrow).

Slide the carpet panel out of the storage compartment (red arrow).
Figure 3

Slide the carpet panel out of the storage compartment (red arrow).

Pull the side trim panel (red arrow) up to remove it.
Figure 4

Pull the side trim panel (red arrow) up to remove it. The right side is shown. Repeat this step for the left side.

Remove the two 10mm storage lid fasteners (red arrows).
Figure 5

Remove the two 10mm storage lid fasteners (red arrows). The right side is shown. Repeat this step for the left side.

Remove the storage lid from the vehicle (red arrow).
Figure 6

Remove the storage lid from the vehicle (red arrow).

The lamp-out warning module is located on the left side of the luggage compartment (red arrow).
Figure 7

The lamp-out warning module is located on the left side of the luggage compartment (red arrow). You can remove some of the tailgate trim fasteners and pull the trim up enough to access and remove the module.

Remove the six tailgate T25 Torx gate trim fasteners (red arrows).
Figure 8

Remove the six tailgate T25 Torx gate trim fasteners (red arrows).

Lift the trim up (red arrow) enough to access the module (green arrow).
Figure 9

Lift the trim up (red arrow) enough to access the module (green arrow). Slide the module off the metal bracket.

To replace the module unplug it and reverse the steps.
Figure 10

To replace the module unplug it and reverse the steps. To test the circuits, continue following the article steps. The circuits and terminal assignments are labeled on the module (red arrow). This will help when using a wiring diagram to identify specific bulb issues.

I always start by checking for power and ground to the module.
Figure 11

I always start by checking for power and ground to the module. First check battery positive, labeled terminal 15 on the module (blue / yellow wire on my vehicle) (red arrow). This should read about 12 volts or whatever your battery voltage is. Then check battery ground, black wire labeled 31. This should read zero volts.

Next, I backprobe and test each circuit to a bulb.
Figure 12

Next, I backprobe and test each circuit to a bulb. I find these to read about 0.5 volts lower than battery voltage with the light switch ON. Go through the bulbs labeled on the module, for example (1999 V70 base), 58LA left parking lamp, 58LB left rear fog / parking lamp, 58A battery positive from fuse C32, 58B battery positive from fuse C24, 58RA right parking lamp, 58RB right rear fog / parking lamp, 58C battery positive from fuse C24, 54H third brake light, 54 brake light switch input, 54R right brake lamp, 54L left brake lamp.

If you want to run through each circuit for bulbs to find a faulty bulb socket or bulb, you can use an incandescent test light to simulate the bulb.
Figure 13

If you want to run through each circuit for bulbs to find a faulty bulb socket or bulb, you can use an incandescent test light to simulate the bulb. Turn the vehicle off. Then connect the test light. Start the vehicle with the test light backprobing the connection. The warning light will got out if the module sees a complete circuit. Connect the test light to ground. Then backprobe each bulb wire at the socket assembly. Use the bulb circuit locations to identify coloring from the notes above. Start the vehicle after each connection. If the warning lamp goes out, you found the faulty circuit. Replace the bulb or socket.

You can also test directly at the module.
Figure 14

You can also test directly at the module. This helps when you can't get the warning light to go out by testing at the socket, and the wiring to the socket is the culprit. If you want to run through each circuit for bulbs to find a faulty bulb socket or bulb, you can use an incandescent test light to simulate the bulb. Turn the vehicle off. Then connect the test light. Start the vehicle with the test light backprobing the connection. The warning light will got out if the module sees a complete circuit. Connect the test light to ground. Then backprobe each bulb wire at the module. Use the bulb circuit locations to identify coloring from the notes above. Start the vehicle after each connection. If the warning lamp goes out, you found the faulty circuit. Replace the bulb or socket.

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