Can Fault Testing In Addition To Repair

Influenza A virus subtype H5N1 Quick Look At CAN Network Testing

A vehicle arrived at our workshop today on the dorsum of the wrecker. The fault reported was non-start as well as equally good the musical instrument cluster was showing a alert that the vehicle was non recognising that the gearbox was inwards neutral.

Although the tests as well as fault finding steps inwards this ship service are the same for almost vehicle CAN networks, the vehicle nosotros were presented amongst was an 2008 Iveco amongst a ZF AS-Tronic EcoLite gearbox.

The outset course of teaching of activity was to behavior out a diagnostic code read on the transmission system, hither are the results:

• Fault Code - 806 - Clutch Actuator
• Fault Code - 830 - Clutch Position
• Fault Code - 833 - Clutch Position Open
• Fault Code - 834 - Clutch Position Closed
• Fault Code - 900 - Terminal 30
• Fault Code - 907 - Relay Circuit 1
• Fault Code - 909 - Relay Circuit 2
• Fault Code - 865 - Gear Select
• Fault Code - 896 - CAN Error Message
• Fault Code - 918 - Clutch Valve 2 Closed

This, coupled amongst the fact that all ability supplies as well as earths were nowadays as well as correct, equally good that other ECUs reported communication errors amongst the transmission ECU, meant that testing of the CAN network at the gearbox was the adjacent step.

The CAN wires are unremarkably slow to position at the ECU harness equally they are usually a twisted pair, silent if you lot convey a wiring diagram for the vehicle available it volition help tremendously.

I monitored the CAN network using a PicoScope silent whatever 2 channel oscilloscope volition create the project as well as should survive setup equally follows.

• Channel 1 or Influenza A virus subtype H5N1 - CAN High
• Channel 2 or B - CAN Low
• 10ms rate
• Channel 1 as well as 2 or Influenza A virus subtype H5N1 as well as B - DC 5v

A quick as well as slow agency to say if the CAN signals as well as wiring to the ECU are inwards working lodge is to disconnect the plug from the ECU as well as mensurate the CAN wires amongst the oscilloscope. In this example the results are inwards the icon below.

Good CAN Waveform

As you lot tin say the CAN waveform is equally you lot would expect. Each moving ridge on the bluish CAN High draw has an equal as well as contrary moving ridge on the crimson CAN Low trace. This tells me that the CAN network is normal as well as working correctly amongst the transmission ECU disconnected. 

The adjacent exam is to reconnect the plug to the transmission ECU as well as monitor the CAN. Here is the upshot from the oscilloscope.

Bad CAN Waveform

In the higher upward icon it is clear that 1 time the ECU has been connected it introduces a definite fault as well as this is almost notable on the crimson CAN Low wire. 

This led me to suspect the transmission ECU was fault as well as the adjacent footstep would survive to withdraw the ECU as well as ship it for testing as well as repair.

Once nosotros received the ECU from the repairers, nosotros reconnected it to the vehicle as well as was able to confirm that the fault had been repaired past times clearing the codes as well as checking that the vehicle started, which it straightaway does!! 

I promise you lot flora this ship service informative as well as straightaway convey a basic agreement of CAN fault finding. 

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