IID Tool from GAP – Diagnosis and Programming

IID Tool from GAP – Diagnosis and Programming

1. September 2020 Off By Kenny

GAP’s IID tool is one of the most powerful diagnostic tools for Land Rover Discovery 3/4 on the market. The tool is plugged directly into the diagnostic socket in the driver’s footwell and communicates via a Bluetooth connection with a corresponding app for the smartphone. The connection is extremely reliable and we have never experienced any problems with data communication. The display on the cell phone is intuitive and simple, the range of functions is enormous.

This article is only a short overview and should not replace the very detailed manual of the IID tool. In addition, this article only describes possibilities without going into the individual risks of each programming. Every programming should therefore be read in the manual of the tool before making any changes here. This overview of functions is generally valid for the Discovery 3/4 – but the system also offers various options for many other vehicles (see manufacturer’s manual).

The manual (English only) can be downloaded from the following link: Handbook


The available functions of the IID tool are divided into the following groups:

  1. Fault Codes – display and delete faults
  2. Live Values – Display of live values
  3. Control IOs – Vehicle Configuration
  4. Service Routines – Parameter adjustment of individual values
  5. Height Control – Adjusting the vehicle height
  6. ECU Info – ECU updates, reprogramming
  7. Extended functions (activation necessary, examples:)

Function description

1. analysis of error codes

In this section all error codes stored in each control unit can be read and deleted. The system can display both the “confirmed errors”, which usually also lead to an error message in the instrument panel of the vehicle, and the “only occasionally” occurring errors that are not shown in the display of the vehicle or the historical and stored errors that once occurred but are no longer present.

The error diagnosis function is virtually one of the most important tasks in finding the cause of problems. Without the information about which component is causing the error, the search for it is much more difficult and unfortunately often very expensive. Nevertheless, error analysis via error code is often not easy and intuitive and requires some experience.

The typical procedure for error analysis in short form is: Read out and interpret the error -> Repair -> Calibrate / perform service routine (if necessary) -> Clear error (if necessary drive a short distance before)

2. live value display

The live value display is an extremely powerful function for analyzing the entire vehicle and identifying problems. The live display can show almost all sensors in the vehicle and also an enormous number of values calculated in the control units. You can also create and save different lists so that you have quick access to the most frequently required values. Listing all values here would be far too much, so here is just a tiny selection of values that can be displayed live. The live display works as a numeric value as well as in the form of a line chart.

In addition, triggers can be programmed, so that certain measurements (or alarms) are automatically triggered when individual values reach predefined limits.

– Vehicle speed
– Speed of each individual tire
– Outdoor temperature
– Fuel temperature after preheating
– Activity of the fuel pump
– Activity of the preheating unit
– Interior temperature in the vehicle
– on-board voltage in the vehicle electrical system
– Activity of the water pump
– Charging current of the battery
– Battery drain current
– Average battery discharge with vehicle parked
– Average battery charge with engine started
– Number of stored battery changes
– Current flow on the battery
– Battery charge status
– Battery Temperature
– Battery voltage
– Volume flow, valve positions and percentage utilization of the interior fans and air conditioning
– Actuator position of each actuator on the air flaps
– Motor speed
– Cooling water temperature
– Temperature of the sucked air
– Volume flow of the aspirated air flow
– Accelerator pedal position from 0-100
– Valve position of EGR valves
– Current motor load
– Main power supply
– Number of events: Water in fuel detected
– Diesel particle filter – differential pressure
– DPF load status
– Oil level calculated and measured
– Exhaust gas temperature behind each cylinder
– Oil quality and pollution factor
– Current vehicle height at each wheel
– Pressure in the chassis distribution (Gallery)
– Compressor temperature
– Engine temperature
– Activated driving program
– door sensor, door status
– Position of each valve of the air distribution in percent
– Steering Angle Sensor Signal
– Rotational speed of steering wheel
– Gearbox temperature, oil temperature
– Selected gear
– Rotation speed output side Gearbox
– Activity of shift paddles
– Pressure in each coupling area
– Torque at output
– and many many many more…


3. control IOs – vehicle configuration

In the Control IO area (control of inputs and outputs) the values of different actuators can be manually changed or overwritten. In doing so, simulated values can be simulated for the control units, which do not correspond to the real values.
The list of values which can be changed here is also very extensive and therefore will not be listed here in detail.


4. calibration of single values / Calibration

There are various systems in the vehicle that are not immediately functional when renewed, but instead require recalibration. These include, for example:
– Steering angle sensor
– Parking brake position
– Yaw Rate Sensor
– Gearbox Calibration
– Coupling calibration
– Calibration of the active attenuation
– Calibration of the air suspension, function is also suitable for levelling the vehicle on uneven ground – e.g. when using a roof tent
– ACC Calibration
– Supported steering

5. height control – adjusting the vehicle height

Various settings can be made in the height adjustment area. The most important ones are reprogramming the height adjustment in the different vehicle modes: Terrain Height, Normal, Highway Height, Entry Height. These settings can be adjusted to almost any value, so that, for example, the normal height already corresponds to the actual terrain height or so that the vehicle can be lowered extremely when the underground car park is very low. When adjusting the height, it is also possible to make corrections that only affect individual axles, for example to correct the slightly wedge-shaped height ratio of the car.
The changed settings can then be stored in a total of 3 different driving programs, so that they can be quickly recalled in the future.

6. ECU Info – control unit

Readout and display of the status and software version of each control unit installed in the vehicle. Installation of software updates for the various control units is also possible.

7. service test

In the Service area, various settings can be made that are necessary when repairing vehicle components. These include, for example:
– Complete (or even only partial) release of the pressure in the airframe from all components (or only one single damper, the reservoir, the gallery) for safe work on the landing gear
– Testing of individual valves of the landing gear by manual switching
– Activate the transport mode (no automatic height compensation)
– Moving the electronic parking brake to the maintenance position
– Delete adaptation values of the motor: All adaptation values that the engine control unit has “learned” over time are reset to factory default. The motor learns everything new
– Manual activation of the fuel pump
– Manual activation of the injectors
– Reprogramming of the injectors – necessary after a replacement
– Diesel particle filter – reset pressure sensor (necessary after replacement)
– Air flow meter – Reset sensor
– Reset oil system – Reset service message
– Turbocharger Reset after replacing the turbocharger
– Reprogramming of the safety identification – after an engine ECU exchange necessary
– Resetting the high pressure pump – after replacement
– Activation of the teach-in program for the engine control unit – necessary after replacing components on the engine
– Activating the automatic fuel line bleeding function
– Resetting the service interval display
– Resetting the self-learning shifting behavior of the automatic transmission
– Teaching new vehicle keys
– Teaching new vehicle batteries after a change
– Resetting the battery monitoring (management) system
– Resetting the Crash Status Counter
– Teaching the window lifters touch function
– Resetting the airbag system (after replacement)
– Teaching the rain sensor (after replacement)
– and much more…

8. car configuration

In the vehicle configuration area, the factory programming of vehicle functions can be changed. The current program is downloaded and saved from the vehicle and then a modified vehicle program is uploaded to the control unit.

In this way, functions can be enabled on the vehicle that the manufacturer has deactivated in the vehicle (for example, because they were not purchased as a paid special accessory). Here is a list of some possible activations, whereby some functions require additional hardware (e.g. monitors in the headrests of “DVD rear seat”):
– Activate 4×4 information display
– Activate rear view camera
– Activate video input
– Change the tire circumference, adjust the speedometer for larger wheels
– Activate Bluetooth
– Activate cell phone function
– Activate multimedia module
– Activate DVD function in the headrests
– Activate luxury display functions
– Activate voice input
– Unlocking the operation of the navigation device while driving
– Activate DVD Player
– Activate mirror fold function
– Enable jogging function of indicators
– Activate TV module
– Activate adaptive headlight system
– Activate high beam assistant
– Activate cornering light
– Enable and activate cruise control
– Activate daytime running light (Scandinavian light or Canadian light)
– Activate fog lights
– Activate memory seats
– Activate rain sensor
– Activate tire pressure control system
– Activate trailer stability system
– Activate Xenon light
– Activate air-conditioned seats
– Activate steering wheel heating
– Activate auxiliary heating (auxiliary heater)
– Calibration of the seat heating to different desired temperatures
– Activate seat heating rear seat
– Activate parking assistance
– Enable automatic release of the parking brake
– Reprogram seat belt reminder
– and many more

Note: The available functions vary greatly depending on the vehicle model. In the instructions, each function is listed after the function for which models this function is possible. You can see an example here in the picture. The L319 is for example the Discovery 4.


Conclusion: Programming devices like the IID tool have an enormous range of functions and are indispensable in vehicles with many electronic helpers. I personally carry the programmer with me on every long trip with the vehicle and would not dare to go on any trip without the tool. With the tool in your pocket you can either fix any errors of the vehicle immediately or you can at least narrow down the exact cause of the error or even completely determine it. Even many independent garages that you find on the road can’t help you because they don’t have the possibility to repair the errors.

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All information as always to the best of our knowledge and belief, but without guarantee!