Troubleshooting/Subaru Liberty Error Code IU
The Problem
My 2006 Subaru Liberty was not driven for six weeks and the odometer displays an error code Er IU.
Also, the cruise control doesn't work but was fine last time I drove it.
Error or fault codes displayed in the odometer area are not well documented. However, by looking at similar problems described by Subaru Liberty or Subaru Legacy owners on Forums, and limited information available from Subaru, I found a simple solution which is documented here.
A list of Subaru Error Codes is also provided at the end of this article.
Like many Subaru drivers I had never previously seen any error codes displayed in the odometer or trip meter section of the speedo. At first I read it as Er 10, but after searching on the Internet found that was incorrect. The code shown in my photo is clearly Er IU.
Apart from the code displayed the vehicle seemed to be performing normally - until I tried to use the cruise control. Nothing worked. No lights, wouldn't switch on, and no ability to set the speed.
My car had been in a workshop for weeks. I suspect that at some time the battery went flat. And it was probably jump-started sometime before I collected it for the drive home.
Explanation
The abbreviation IU refers to the Body Integration Unit - in other words, one of the car's computers.
If the code Er IU is interpreted to mean that the Body Integrated Unit itself is faulty - some dealers or mechanics suggest this - then it would need to be replaced at considerable expense.
However, it is more likely that the Body Integrated Unit is operating correctly and just showing that it has detected a problem. One condition likely to trigger that is a flat battery. But there could be other faults in any of the systems monitored by this Unit - such as the central locking system, windshield wipers etc.
As a safety feature, if the Body Integration Unit detects an error it will disable the cruise control system so that the driver remains in full control of the vehicle.
Solution
Based on advice given by other Subaru owners I tried the following steps:-
- Disconnect the earth cable from negative terminal on the battery.
- Wait at least one minute. Some people suggested up to 15 minutes.
- Reconnect the battery. If the battery is not fully charged, fix that first.
Note: The positive battery terminal should be covered, not as shown here.
It's Fixed!
After reconnecting the battery the error code has disappeared.
Also, when I selected cruise control the light on the instrument panel shows that it is operational.
Prior to going through the above steps I had driven for about 100 km, so the battery would have recharged.
If you have the same problem, I hope this simple solution works for you.
Grant
Other Subaru Error Codes
Unfortunately, if you have a different error code the solution is likely to be more complex and you may need to visit a Subaru Dealer.
Related codes are listed in the Table below, and you may find helpful diagnostic information from the sources which have been linked.
| Error Code | Description | Comments |
| Er IU | Malfunction in Body integrated unit | As this article shows, the code may indicate an abnormality detected by the Body Integrated Unit, not a failure of the unit itself. Try the solution described above! A variation on this code is shown below:- |
| Er IU | Body Integrated Unit failed | Abnormality is found in the integrated ECM or in its related parts. |
| Er -- | Simultaneous malfunction (failure) of both high speed CAN and low-speed CAN communication | The CAN system uses two different data rates - see Note 2 below |
| Er HC | Malfunction (failure) of high-speed CAN communication | The high speed CAN manages power units |
| Er LC | Malfunction (failure) of low-speed CAN communication | The low speed CAN manages body units |
| Er EG | EGI Communication malfunction or EGI communication data abnormal or Engine control module communication counter failure | Subaru uses the acronym EGI which may mean electronic gasoline injection. The more common name for the computer controlling a fuel-injected engine is the ECU. |
| Er TC | TCM Communication malfunction or TCM communication data abnormal. Abnormality is found in the TCM ECM or in its communication system | TCM is the Transmission Control Module. The error may also be shown as Er tC |
| Er Ab | ABSCM/VDCCM Communication malfunction or ABS/VDC control module communication counter failure | ABS is the Anti-Lock Braking System - ABSCM is the ABS Control Module VDC is the Vehicle Dynamics Control system - VDCCM is the VDC Control Module Abnormality is found in the ABSCM/VDCCM & H/U unit or in its' communication system. |
| Er SP | ABSCM/VDCCM DTC information, vehicle speed pulse malfunction or Vehicle Speed Signal abnormal (ABS/VDC diagnostic trouble code information) | DTC is the Diagnostic Trouble Code |
| Er SS | Wheels speed data malfunction or wheel speed signal abnormal) | Many people incorrectly read this as Er 55. SS means Speed Sensor, or more accurately an ABS wheel speed sensor. |
Note: This table was compiled from documentation for Subaru Liberty/Legacy and Imprezza, available here and here.
Notes
1. CAN Bus
An article Automotive Controller Area Network System by Automotive Engineer Kiril Mucevski describes the CAN Bus:
The Controller Area Network (CAN, also known as CAN Bus) is a vehicle bus standard designed to allow electronic control units and devices to communicate with each other in applications without a host computer. As an alternative to conventional multi-wire looms, CAN Bus allows various electronic components (such as: electronic control units, microcontrollers, devices, sensors, actuators and other electronic components throughout the vehicle) to communicate on a single or dual-wire network data bus up to 1 Mb/s.
2. High and Low Speed CAN
The Subaru Liberty/Legacy has a Local Area Network (LAN) which enables the different computer modules to share data using the CAN system. Two data rates are used:-
- High-speed CAN running at 500 Kbps, which manages power-related units
- Low-speed CAN running at 125 Kbps, which manages body-related functions.
The body integrated unit has a gateway function which enables data sharing between the two different-rate networks.
Source: Extract from Subaru documentation
3. Combination Meter
Subaru documentation refers to the instrument panel - tacho, speedo, gauges, warning lights - as a Combination Meter.
4. Fault Detection
Subaru documentation describes the detection of faults and display in the combination meter:-
- If a fault occurs in the body integrated unit or LAN system (in any unit or the communication circuit), a communication error indication is given at the trip information display area on the combination meter.
- The indication differs by the type of fault, and related indicators such as the CHECK ENGINE light illuminate.
- If a communication error indication is given, one or more diagnostic trouble codes are stored in the body integrated unit. To read out diagnostic trouble codes, use a Subaru select monitor.
- If more than one diagnostic trouble code is stored, indication is given in the following order of priority:
(1) High-speed CAN (2) Low-speed CAN (3) integrated unit (4) EGI (5) TCM (6) VDC
5. Diagnostic Trouble Codes
The scope of this article does not include the Diagnostic trouble Codes (DTC) as there is already a lot of information available.
Subaru documentation refers to reading the DTCs with a Subaru select monitor which is an official code reader.
For the error code Er IU it is unlikely that a DTC would remain stored. For all other problems the Error Code in the trip meter or odometer is an indication that something more serious has occurred and you should read the diagnostic trouble code to determine the exact cause. Or take the vehicle to a reputable Dealer.
