Hi all, i have a question on Transfer Case live data that is available on the GAP IId Diag tool. The tool is plugged into an O7 RR L322 SC. Here is the punch line, if i am interprting the live data correctly, the engine thinks the Transfer box is in Low while the transfer box thinks it is in high. If this is the case, it adds a piece of data to the RR being in Limp Mode, assuming i am interpreting them correctly. See below

If the car is in Low Range, I get the follow live data: (see screen shot too)
Transfer case control module - output status - low range LED.... ON
Transfer case control module - output status - high range LED.... OFF
Transfer case control module - output status - Gear - Low Range.... Yes
Transfer case control module - output status - Gear - High Range.... No
Engine input 2 - transfer box range - actual.... High

If the car is in High Range I get the follow live data (see screen shot too)

If the car is in Low Range, I get the follow live data:
Transfer case control module - output status - low range LED.... OFF
Transfer case control module - output status - high range LED.... ON
Transfer case control module - output status - Gear - Low Range.... No
Transfer case control module - output status - Gear - High Range.... Yes
Engine input 2 - transfer box range - actual.... Low

The way i read this is that the engine thinks the RR is in Low Range, when the transfer case thinks it is in High Range. I am interpreting Engine input 2 correctly?

If this is really the case... any ideas on how this can happen? My limited understanding is that the Transfer Case Control Module communicates with the ECM via the High speed CAN.

Last edited by jriedel on 14th Oct 2022 6:37am. Edited 1 time in total

As the engine is shown as reporting low range for both high range and low range, there could be a bug in the reporting. My IIDtool reports my 8-speed gearbox as a 6-speed.

I corrected a typo above, it is now correct, the engine reports high when transfer reports low, and reports low when transfer reports high.

If your IIDtool isn't at the latest level then best to update it in case a bug has been corrected, but comparing with the same logging done on another vehicle would seem appropriate.
What values did you monitor? I can check what mine shows.

I would love to see what another RR show for these same live values.

I purchased the Gap Tool BT about a month ago and went through the activation and update procedure, but i will see if i can check the software version are the latest.

The first 4 values are in Transfer Case Control Module (TCCM) and the last is under PCM. Here is a screen shot of both conditions.

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Is there a clue with the car's behaviour?
What is the problem that you're trying to fix?
What trouble codes are being logged?

DTCs... I thought you would never ask
From the start, I will say I hope most, if not all these DTCs, are cascaded from one particular needle in the proverbial haystack.

When the ignition is switched to position 2 the Main Message Center reports
1) Engine System Fault
2) Transmission Fault - Limited Gears Only
3) HDC Fault - System not Available

The vehicle will start and idle. Idles around 1000 rpm for a few minutes, than converges on 800ish rpms
The vehicle does not go into closed loop control, I believe.

MIL for Battery Turns On - Red
MIL for Brake Turns On - Yellow
MIL for Check Enginer Turns On - Yellow
MIL for Dynamic Stability Control Turns On - Yellow

I have checked the CAN system resistance from the OBD2 port (Pin 6 and 14), I get 60 ohms. Two 120 ohm resistors in parallel (one in ABS Unit the other in Parking Brake Module).

I have checked the CAN High and Low Signals with an Oscilloscope,
a) CAN High between 2.5 and 3.5 VDC
b) CAN Low between 1.5 and 2.5 VDC

I have checked current to an from the Battery during idle with accessories off and on (i think i see what is turning on the Battery light, but not sure if the cause is the Alternator's response or the Engine Control Module's command)
Accessories off
Battery Voltage = 13.6- 13.7
Current to Battery from Alternator = 1.5 Amps
Current from Battery to Vehicle = 1.5 Amps

Accessories On (seat heaters, headlights, blowers, Radio)
Battery Voltage = 13.6 - 13.7
Current to Battery from Alternator = 1.5 - 2.0 Amps
Current from Battery to Vehicle = 4 - 5 Amps

Checked all fuses in and relays (for resistance low current side and high current side)
1) Engine Junction Box
2) Auxiliary Junction Box

Checked All Fuses in Central Junction Box.

Have checked for grounding and Continuity at various location, but in an attempt to keep this post short i digress.

There are a bunch of DTCs, here are screen shots from the
1) ATCM - Terrain Response
2) PCM - Engine Petrol
3) TCM - Transmission
4) VDM - Vehicle Dynamic
5) IPC - Instrument Pack

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There appears to be a power supply issue with the PCM, possibly a short circuit on a sensor 5V supply. I would check the wiring to all the listed sensors looking for chafing.

Sounds like a good project for tonight, thanks for the advice. I'll let circle back with what i find.

GraemeS wrote:

There appears to be a power supply issue with the PCM, possibly a short circuit on a sensor 5V supply. I would check the wiring to all the listed sensors looking for chafing.

Started checking the things that are connected to the PCM that threw codes
Ebox related Code
1)Tested to the connections to the ebox fan.
2)Removed the ebox fan and bench tested it at 12.6 VDC. It sounds fine and it draws about 150 - 200 mA when running.


Throttle body - Forced shutdown Code
1) Backprobed Throttle body connector: Checked 5 volt reference signal to ground, yes it is 5 vDC
2) Backprobed Throttle body connector: while vehicle is Idling, Measured Sensor 1 voltage at 0.85 VDC, measured sensor 2 voltage at 1.7 VDC.
3) Connected throttle body to an external 5 VDC power supply, rotated butteryfly to see if voltage changed. It does, but i am not sure if it is changing like it is "supposed to". From closed to vertical, voltage goes from 0.85 to 4, and 1.7 to 4.3 on position sensor 1 and 2 respectively.
4) Measured resistances across position sensors as I rotated buttery fly in throttle body. Oddly, the resistances don't change (i figured they would, since my understanding is they are potentiometers). The image below shows the resistance values that I measure.

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I am going to post this throttle body info/questions in a new post.