Instrument Cluster Lights Not Working

[Zach]

I have a 1999 Chevy Silverado 1500. And the back lights to the Tachometer, Speedometer, gas, oil, battery, and Temp Gauges do not work, as well as the back light to my climate Control. The Gauges themselves work fine as well as the Climate Control but the Lights don’t. I have Replaced the Dimmer Switch/ Headlights Switch, the entire Cluster itself, Checked and rechecked the fuzes and bulbs, and the DLR (Day Light Running Lights) Sensor and everything seems fine. I bought the truck with the dash lights already out and not working, he did install a aftermarket stereo. I have looked behind to see if there are any grounds or bare wire and it seems ok (i haven’t done a full detail check, but i have taken the stereo out and looked around). I have a Video on youtube showing you if you need some visual http://www.youtube.com/watch?v=eWADNPiUpac . Any ideas????

Topic

[Monte Hyler]

Have you worked through the wiring diagram on this? Sounds like a bad connection somewhere along the way.

[dave]

Here are three TSB’s that might address ye’ problem:

Here is a copy of the ground distribution of your interior driver amenities. Although there are a lot of devices tied into a common ground, there does not appear to be a correlation between the radio and the instrument panel cluster:

Here is the power distribution to the instrument panel cluster. It appears that the IPC gets power from circuit #1020 via a pink .35 gauge wire spliced from the ‘TRANS’ (fuse #20) 10amp fuse, delivered through ‘pin #7’ via a female connector to the IPC:

Attachments:

• S298.png
• tsb5.png
• tsb7.png
• pwr2.png
• tsb1.5.png

[Zach]

Is it the wiring ignition switch/starter or just the Ignition Key Switch/Lock?

[dave]

Is it the wiring ignition switch/starter or just the Ignition Key Switch/Lock?

I don’t know. I need more information. Basic electrical testing needs to be performed.

Based on the TSB’s recommendations as well as my own knowledge of basic electrical theroy, I have devised a general strategy to help remedy your problem with the IPC and HVAC temperature control head:

• Remove the 2 aforementioned devices from the dash
• Disconnect the electrical connections
• Test for power to the devices

If power:

• repair or replace failed device(s)

If no power:

• check battery voltage
• verify fuse continuity
• turn ignition key to ACC
• disconnect and reconnect all associated wiring harnesses (as per TSB)
• Perform ‘wiggle test’ on all wiring harnesses
• visually inspect wiring for a possible open in the circuit. if an open cannot be detected, splice into known good circuit close to the fuse box and run a parallel line to the associated affected device(s)

[u]

One more additional test[/u]:
One thing that I wasn’t sure if I wanted to include in the above list is to check the affected non-working devices by applying power directly to the affected circuits/devices from an outside source and see if they light up.

Final thoughts:
I like the TSB stating that it might just be an open in the ignition switch. I believe it would be worth your time to perform the testing on the ignition circuit as stated in the TSB. It is quite possible that you are only 1 ignition lock cylinder away from restoring your lights. 🙂

One thing that all your affected devices have in common is the dimmer rheostat. Perhaps it is possible that the dimmer is stuck in a ‘off’ or ‘low’ setting and has since been rendered unresponsive. I’m going to try to do some further study to see how it can be tested. I might have to utilize my school’s resources though, so I might not respond until sometime tomorrow.

Q: Does the interior dimmer rheostat have an affect on any other interior lighting?

[R.G.Young,Jr]

I assume that no dash lights are working, is that correct? if it is, also check to see if the tail lights are working. the tail lights and the dash lights are usually on the same circuits.if the tail ligths are working ok then you may want to start your testing with dash grounds. voltage drop testing can confirm their integrity. if all of the lights are inopertive including the tail lights , then you most likely have a power issue.
Keep posting and good luck.

[dave]

Now that I have access to school resources, I now have a good schematic for the IPC:

IPC Description and Operation

INSTRUMENT CLUSTER
The standard instrument cluster contains a microprocessor. The instrument cluster micro processor communicates with other modules in the vehicle over the Class 2 serial data line. The information passed over the Class 2 serial data line, along with dedicated circuits to specific sensors and modules, provides the inputs which are used to operate all the gauges, indicators and the message center in the cluster. The instrument cluster continuously processes class 2 serial data in order to determine the correct values and states to display. When replacing instrument panel cluster assembly, federal law requires that the odometer reading of the replacement unit be set to register the same mileage as the prior odometer. If the same mileage cannot be set, the law requires that the replacement odometer be set at zero and a label be installed on the drivers door frame to show the previous odometer reading and the date of replacement.

The instrument cluster includes the following components:

• Gauges Indicators
• Message center
• Tachometer
• Speedometer/Odometers
• PRNDL

Interior Lights

NON-DIMMABLE LAMPS
Voltage to the coil of the courtesy lamp relay, dome, reading lamp, courtesy lamps, cargo Lamp, Instrument Panel (IP) compartment lamp and the underhood lamp is supplied from the Inadvertent power relay on CKT 1732. The inadvertent power relay receives voltage from the CTSY LP fuse which is hot at all times. Ground for the courtesy lamps goes through the courtesy lamp relay. Both relays are controlled by the Body Control Module (BCM) based on inputs from door jamb switch, dome lamp switch or door handle switch. The BCM will supply a ground to the courtesy lamp relay when closing any one of the above switches to ground. Ground for the reading lamp, cargo lamp, IP compartment lamp and the underhood lamp is supplied by its own ground.

Voltage to the ash tray lamp and power window/door lock switches is supplied from the INT PRK fuse. Voltage to the INT PRK fuse is supplied from the park lamp relay, and is hot when park lamps or headlamps are on.

DIMMABLE LAMP
With the headlamp and panel dimmer switch in the park or head position, voltage is supplied to the IP dimmer switch via CKT 44. The voltage output of the IP dimmer is veritable and goes through the ILLUM fuse via CKT 8 to the cluster, radio and various IP switches. For the radio and cluster displays and some switches, an additional circuit is required, CKT 1382, for the these components to dim. CKT 1382 is a 12 volt output of the BCM, and is hot when park or headlamps are on.

Some circuits are monitored by the BCM, and upon failure may set a DTC.

Interior Lighting Schematic:

Dimmer Switch Schematic:

Attachments:

• ipc.png
• interiorlights.png
• dimmerswitch.png

[Zach]

The information/message lights will work on the dash (such as check engine lights/seat belt light etc. Just not the lights to the Volts,Fuel,Temp,Oil,Tachometer,and Speedometer. Also my Tail lights are working.

[Zach]

@Wrench Turner, ill be sure try that. but how would i test to see if im even getting power to the IPC and climate control head?

[dave]

[quote=”ZachSyndy” post=54813]The information/message lights will work on the dash (such as check engine lights/seat belt light etc. Just not the lights to the Volts,Fuel,Temp,Oil,Tachometer,and Speedometer. Also my Tail lights are working.[/quote]

General Information

The Instrument Cluster (IPC) indicators are illuminated by one of the following methods:

The IPC detects a concern with a discrete input.
A module sends a indicator illumination request message, via the class 2 serial data line.

Could be a problem in the communication bus… possible dead, babbling, or disruptive module.

[Zach]

what the communication bus?

[dave]

Ignition Lock Cylinder

This article updated with TSB 02-02-35-001.

IGNITION LOCK CYLINDER REPLACEMENT – ON VEHICLE

REMOVAL PROCEDURE

Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

For Vehicles equipped with OnStar (UE1) with Back Up Battery:
The Back Up Battery is a redundant power supply to allow limited OnStar functionality in the event of a main vehicle battery power disruption to the VCIM (OnStar module). Do not disconnect the main vehicle battery or remove the OnStar fuse with the ignition key in any position other than OFF. Retained accessory power (RAP) should be allowed to time out or be disabled (simply opening the driver door should disable RAP) before disconnecting power. Disconnecting power to the OnStar module in any way while the ignition is On or with RAP activated may cause activation of the OnStar Back-Up Battery (BUB) system and will discharge and permanently damage the back-up battery. Once the Back-Up Battery is activated it will stay on until it has completely discharged. The BUB is not rechargeable and once activated the BUB must be replaced.

Set the front wheels in the straight-ahead position.
Set the steering wheel in the LOCK position.
Disconnect the negative battery cable. Caution: When you are performing service on or near the SIR components or the SIR wiring, you must disable the SIR system. Failure to follow the correct procedure could cause air bag deployment, personal injury, or unnecessary SIR system repairs.
Disable the Supplemental Inflatable Restraint (SIR) system. See: Air Bag(s) Arming and DisarmingService and RepairDisabling the SIR System
Remove the tilt lever.
Remove the 2 TORX head screws from the lower steering column shroud.
Remove the lower steering column cover shroud from the column.
Remove the TORX head screw from the upper steering column shroud.
Remove the upper steering column shroud from the column.

Turn the ignition lock cylinder to the START position.
Using an awl, insert the tip into the ignition lock cylinder access hole (1).
Push down and hold the ignition lock cylinder retaining pin.
Release the ignition lock cylinder to the RUN position.
Remove the ignition lock cylinder by pulling the ignition lock cylinder away from the steering column (2).

INSTALLATION PROCEDURE

Install the ignition lock cylinder into the steering column (2) using the following procedure:
1.1. Align the positioning locking tab slot on the lock module assembly to the positioning tab on the ignition lock cylinder.
1.2. Push the lock cylinder in until the locking tab locks in the lock module assembly.

Install the upper steering column shroud to the steering column.
Install the TORX head screw to the upper steering column shroud. Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
Tighten the screw to 1.5 Nm (115 inch lbs.) .
Install the lower steering column shroud to the steering column.
Install the tilt lever.
Install the TORX head screws to the lower steering column shroud.
Tighten the screws to 3 Nm (25 inch lbs.) .
Enable the SIR system. See: Air Bag(s) Arming and DisarmingService and RepairEnabling the SIR System
Connect the negative battery cable. Perform the Idle Learn Procedure. See: Testing and InspectionPowertrain Control Module (PCM) – Idle Learn Procedure Perform the PASSLOCK Reprogramming Auto Learn. See: Testing and InspectionPASSLOCK – Reprogramming Auto Learn

Attachments:

• st1.gif
• st2.gif
• st3.gif
• st4.gif

[Jim]

i think its a power or ground issue. think ur on the right track with the wireing from that aftermarket radio. look how the ground is shared for the HVAC and I P lights on that splice pack 203. but most importantly look how they both share that INT PRK fuse in that left bussed electrical center. i would double check that fuse isnt blown. if that fuse is ok i would pull out either the cluster or the HVAC controler and check for power at the respective pins. if thats good then check the ground. let me know if you need some help.

[Author]

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