Alright so here is the diagnostic sheet I came across for a Deville
DTC B1390 -The DIM has an internal battery voltage sensor and a reference voltage. The DIM compares these two voltages via the two battery positive voltage circuits every 300 milliseconds. Do you know what the DIM is ?
Conditions for Setting the DTC
This code shall be set after 10 consecutive readings that the two battery positive voltages differ by 1 volt or greater.
Turn OFF the ignition.
Disconnect the dash integration module (DIM).
Turn ON the ignition, with the engine OFF.
Measure and record the voltage from both battery positive voltage circuits of the DIM to both ground circuits of the DIM.
Compare the two recorded DIM battery positive voltage circuit voltages.
Is the voltage difference less than the specified value?
1 V
YES - Go to Step 5
NO - Go to Step 3
These are the results of my vehicle as measured:
Main Power to Main Ground: 11.3 V
Main Power to Reference Ground: .7 V
Reference Power to Main Ground: 10.8 V
Reference Power to Reference Ground: .6 V
I don't know the "specified value" here but these seem to check out as making sense to me. Please correct me if I'm wrong but this seems to confirm no wiring issue. Onto Step 5
Test both DIM battery positive voltage circuits for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES - Go to Step 7
NO - Go to Step 4
4
Test both DIM ground circuits for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES - Go to Step 7
NO - Go to Step 5
5
Inspect for poor connections at the harness connector of the DIM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
YES - Go to Step 7
NO - Go to Step 6
Connections are fine. Onto step 6Important:: After replacement of the DIM perform the set up procedure for the DIM. Refer to Body Control Module (BCM) Programming/RPO Configuration .
Replace the DIM. Refer to Dash Integration Module Replacement .
Did you complete the replacement?
So I taking this to mean I should find a replacement DIM here? That's the gist I'm getting from this test--
YES - Go to Step 7
--
7
Use the scan tool in order to clear the DTCs.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.
Does the DTC reset?
--
Go to Step 2
System OK
Do you know what there saying here ? Do you know where The DIM is located . Do you know where to find a wiring diagram so you know what your testing ?
free wiring diagrams at
http://www.bbbind.com/free_tsb.html Enter vehicle info year , make , model ,engine . under system click on body & accessories, then under sub system click on body controls . Hit the search button a blue link will pop up . click on that .
Dash Integration Module (DIM)
The various DIM input and output circuits are described in the corresponding functional areas as indicated on the DIM electrical schematics.
The DIM functions include the following:
• Class 2 communication requiring DIM interaction.
• Control of exterior lamps.
• Control of front fog lights.
• Control of the headlights.
• Headlamps on with wiper input.
• Hood ajar switch input w/export.
• Horn relay control.
• Interior lamps incandescent dimming.
• Low side temperature for HVAC compressor.
• Power moding control over Class 2 serial data circuit.
• Reverse lockout solenoid control.
• Steering wheel controls input.
• Storage of the clock settings and, sending a message out on the class 2 serial data circuit in response to requests from other modules. Good luck !