Service 4WD Light ????????
09-21-2006, 01:31 PM
#1
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Service 4WD Light ????????
I have a 00 Silverado and lately the big yellow SERVICE 4WD light has been coming on 
. What causes this, is there anyway to pull a code on it other than take it GM and what is the most common reason why. Any help would be greatly appriceated.
. What causes this, is there anyway to pull a code on it other than take it GM and what is the most common reason why. Any help would be greatly appriceated.
09-21-2006, 06:43 PM
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...Or about $65 at the dealership. It is a very common problem, when the light comes on next time look at your 4wd switch and see is the little light is on 2hi, if there is no light, the switch is bad.
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09-22-2006, 06:08 PM
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On the older ones <99-02> it was usually the switch that caused the prob, on the newer ones with Auto4WD <03-06> its more than likely the encoder motor or its called the transfer case actuator. Autozone will probably NOT be able to pull it since its not in the PCM<engine computer>but hey Ive been wrong before its worth a shot.
09-22-2006, 06:50 PM
#9
It was the switch on my '04. Does anything happen when you select the various modes with the switch. When my switch was bad it wouldn't do anything. I only had 2WD. Off course it had to happen during a snow storm!
From the '00 service manual:
Service 4WD Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch) #02-04-21-004 - (Apr 15, 2002)
"Service 4WD" Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch)1999-2002 Chevrolet and GMC C/K Pickup and Utility Models (Silverado, Sierra, Avalanche, Suburban, Tahoe, Yukon, Yukon XL)
with Four Wheel Drive and NVG 236/246 Transfer Case (RPO NP8)
Condition
Some customers may comment on the Service 4WD indicator illuminating. Upon investigation, the technician may find DTC B2725 set.
Cause
The condition may be due to a intermittent fault in the transfer case shift control switch.
Correction
Important
The transfer case shift control module should not need replacement. DO NOT replace P/N 15749703 unless diagnosis points to the module as the malfunction.
From the '00 service manual:
Service 4WD Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch) #02-04-21-004 - (Apr 15, 2002)
"Service 4WD" Indicator Illuminated, DTC B2725 Set (Replace Transfer Case Shift Control Switch)1999-2002 Chevrolet and GMC C/K Pickup and Utility Models (Silverado, Sierra, Avalanche, Suburban, Tahoe, Yukon, Yukon XL)
with Four Wheel Drive and NVG 236/246 Transfer Case (RPO NP8)
Condition
Some customers may comment on the Service 4WD indicator illuminating. Upon investigation, the technician may find DTC B2725 set.
Cause
The condition may be due to a intermittent fault in the transfer case shift control switch.
Correction
Important
The transfer case shift control module should not need replacement. DO NOT replace P/N 15749703 unless diagnosis points to the module as the malfunction.
Last edited by DrX; 09-22-2006 at 07:42 PM.
09-22-2006, 07:24 PM
#10
Could also be the t-case shift control module as per the service manual:
SERVICE 4WD Message Always On
Test Description
The numbers below refer to the step numbers on the diagnostic table.
(#2 Determines whether the failure is the result of a faulty transfer case shift control module or the instrument cluster.)
SERVICE 4WD Message Always On
1. Was the Transfer Case Diagnostic System Check performed?
Yes=Go to Step 2
No=Go to Diagnostic System Check
2. Turn ON the ignition, with the engine OFF.
Yes=Go to Step 3
No=Go to Instrument Panel Cluster (IPC) Replacement
3. Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .
Is the repair complete?
Yes=Go to Step 4
4.
1. Use the scan tool in order to clear the DTCs
2. Operate the vehicle within the Conditions for allowing the symptom
to re-occur.
Does the symptom re-occur?
Yes=Go to Step 2
No=System OK
SERVICE 4WD Message Always On
Test Description
The numbers below refer to the step numbers on the diagnostic table.
(#2 Determines whether the failure is the result of a faulty transfer case shift control module or the instrument cluster.)
SERVICE 4WD Message Always On
1. Was the Transfer Case Diagnostic System Check performed?
Yes=Go to Step 2
No=Go to Diagnostic System Check
2. Turn ON the ignition, with the engine OFF.
- Install a scan tool.
- Use the scan tool in order to command the SERVICE 4WD Message OFF.
Yes=Go to Step 3
No=Go to Instrument Panel Cluster (IPC) Replacement
3. Replace the transfer case shift control module. Refer to Transfer Case Shift Control Module Replacement .
Is the repair complete?
Yes=Go to Step 4
4.
1. Use the scan tool in order to clear the DTCs
2. Operate the vehicle within the Conditions for allowing the symptom
to re-occur.
Does the symptom re-occur?
Yes=Go to Step 2
No=System OK
Last edited by DrX; 09-22-2006 at 07:46 PM.
