My RR dropped into the transmission failsafe mode yesterday. I limped home and used my Gap IIDTool and got the following results. After clearing the fault codes, she worked fine for about 5 minutes, then dropped into the transmission failsafe mode again. Does this look like a gear box mechanical fault or an ECU/control box fault?

Cheers

Gary

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L322 - Range Rover 2004
Vehicle scanned on 15-10-2025 16:20
Using IIDTool BT V4.0 B4138

IP-Instrument Pack

0xBF Instrument Pack checksum incorrect
0x8D Transmission Interface Bus fault

LCM-Light Control v12+

0x57 Air suspension active/inactive
0x59 Transmission emergency program fault

TCM-Transmission

0x36 Gear monitor 4 fault: General fault
0x30 Mechanical torque converter monitor fault: General fault

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Transfer case range change potentiometer cracked solder joints - although you don't seem to have the common error messages for that.

Waiting RRPhil to chime in with expert advice. Ron B. VK2OTC
2003 L322 V8 Auto
2007 Yamaha XJR1300
Previous: 1983, 1986 RRC; 1995, 1996 P38A; 1995 Disco1; 1984 V8 County 110; Series IIA

Hi P38,

Thanks, I'll have a look at that once I have checked in RAVE where this potentionmeter is!

I find it frustrating that the GAP Tool produces Hex codes like this, rather than P-codes for diagnosing faults. It means that we only have their descriptions to work from, and not the proper codes.

“0x36 Gear monitor 4 fault: General fault” may mean P0734

Similarly, “0x30 Mechanical torque converter monitor fault: General fault” may be P0741 (stuck off), P0742 (stuck on) or P0743 (TCC PWM solenoid circuit issue)

Does anyone know how to translate these IIDTool codes?

Although there may be a mechanical issue with your torque converter lock-up clutch it’s worth ruling out the solenoid and its wiring first. Without any further clarification of the fault codes, I would begin by checking the resistance between pins 3 & 6 at the C1835 transmission ECU connector, to check the integrity of the TCC PWM solenoid and its wiring. You should get a reading of between 10.0 & 11.5Ω