This 2005 Chevrolet Suburban came in with the complaint that the instrument cluster gauges do not work. I asked the customer how the problem had started and he told me that the speedometer has been acting up for a while. Recently all of the gauges stopped working at the same time. I connected my Tech 2 scan tool and checked IPC codes and data. The IPC would not communicate at all. In checking power supplies to the IPC on a wiring diagram I found that thee are multiple designations for the battery all the time and ignition fuses. The continuous battery fuse may be labelled IPC/DIC, 10 amp or SEO B1, 15 amp. The ignition fuse may be labelled IGN E or SEO IGN. Both are 10 amp fuses.
The troubling thing is all four are listed in the fuse box legend. I checked the IPC/DIC fuse as shown below.
The IGN E fuse tested good as well. The key had to be good in order to confirm power was present on both legs of the fuse. Since the other two fuses were also installed in the fuse box I checked those as well and the too were okay and had the proper power signal present.
Now I had to check for the same power conditions at the wiring harness behind the instrument cluster. The next step was to remove the dash trim panel that covers the IPC. I always start by grasping the outer edge of the panel and pull it out to release the spring clips.
The steering column will need to be tilted fully down and the shifter placed in the lowest gear setting. Then the trim panel has to be carefully rolled out of the dash. The hazard switch will likely pop up and will have to be turned back off.
Four screws hold the IPC in place and they all have 7 mm heads. Once the screws are removed the cluster can be rolled towards the steering wheel and the harness disconnected.
The IPC harness connector.
Battery power is supplied on the orange wire, terminal B11.
Ignition power is supplied on the pink wire, terminal B9.
There are two ground wires, terminal A12 and terminal B12. Both wires are black and one has a white stripe.
I alternated using the A12 and B12 terminals for a ground and tested power at both B9 and B12 using a jumper wire assembly with a halogen headlight bulb installed. This provides a load on the circuit. I often will use a fused jumper wire with the factory rated fuse installed and I install a slightly higher amperage fuse in place of the original factory fuse for the circuit. I actually prefer that as it will accurately tell me if a wire pair will carry the factory rated amperage. In this case 10 amps. Hard to capture the fuse blowing on camera though. Either one of these tests are not for the faint of heart or the uneducated. The bulb can shatter, melt plastic or burn skin. Jumping power and ground circuits can immediately destroy components, releasing the magic smoke that allows all electronics to function.
The next step was to isolate the data communication line between the IPC and the splice pack the the lower left of the dash assembly. I removed the white buss bar and located the gray wire at terminal “G”. I installed a test lead to insure a good connection.
I checked for a short to power or ground using my ohm meter, okay.
I then checked continuity from the IPC terminal A6 to the splice pack terminal “G”. It too was okay.
Diagnosis of a faulty instrument cluster assembly. Replacing the IPC involves some programming and that is a topic for another day.
The condition that you are referring to is “Logic Lock” and I am quite familiar with it. It did not apply to this vehicle but I appreciate you bringing it up.
Sparky
Electrical problems chevy tahoe; is the computer have to reset. to reset you can do two things disconnect the battery cables and put them in so that capasitores cortosircuito are unloaded or put a ground wire to the housing cumputadora and then take it off and go. Computer was left locked in time that’s the problem.
Great info! Excellently explained. Thank you