Car woes

[Islander71]

I have a mk1 Santa Fe 2.0crdi which has been a good car over the 3 years I've owned it, now with 178,000 miles on it. A few weeks ago it started not starting - immobiliser problems - but eventually after inserting and removing the only key it has always started. Cleaned the connections from the immobiliser coil to immobiliser connector which I think has helped, but a couple of days ago it cut out while driving. Its now done this repeatedly. It turns out if the revs go to near 4,000 it just cuts the engine and shows a fault code U0008 high speed canbus high. The engine also runs on for a second or two after turning off the ignition which its never done before. It is still driveable, just, if I keep the revs low, though I think down a bit on power.
Yesterday I took apart all connectors I could find including the ECU ones and sprayed with contact cleaner before reconnecting, tried disconnecting the battery for a couple of hours, have tried erasing the fault code, ( have a basic OBD reader) but nothing has worked. Cann't see any chaffed wiring, but there are an amazing number of bundles of fine wiring. I am now at a loss as to what to do as I dont think there are any auto-electricians on the island. Is it time to scrap it or does anyone have any suggestions as to what may be the problem?

 

[malcolm]

Are there any features that don't work? Radio / sat nav / electric seats etc? Could try disconnecting any ecu/module that doesn't work in case one of them is bringing down the CAN bus.

Worth a look in areas where water can sit and where they stuff ECUs or connectors. I had a CAN fault due to a wet connector under the floor carpet. ECUs under seats or under the front carpet can get wet as can anything in the sides of the boot. Worth an inspection in those areas.

 

[jsf55]

Have you checked the battery for quality ? and how about the battery in the key remote if it has one ?

 

[dobbslc]

Worth a look at all the battery leads and connections and check the battery voltage.
It sounds a bit like you have two different faults here with the immobilizer then a fuel problem.

 

[Islander71]

I did think it likely it is 2 separate faults, but funny they have both occurred fairly close together, and the immobiliser does stop the fuel injection. I think the battery in the key fob is only for the remote door locking, not the immobiliser. The starter battery is fairly new and heavy duty, but I will double check leads, and look at connections again. I do keep it garaged so the inside stays dry., but will look under seats just in case. Good point to check if anything else has stopped working - haven't noticed anything, but will check. Was impressed by how clean and bright all the connectors I have taken apart have been - the car is 19 years old, but they all looked brand new.

 

[premmington]

I did think it likely it is 2 separate faults, but funny they have both occurred fairly close together, and the immobiliser does stop the fuel injection. I think the battery in the key fob is only for the remote door locking, not the immobiliser. The starter battery is fairly new and heavy duty, but I will double check leads, and look at connections again. I do keep it garaged so the inside stays dry., but will look under seats just in case. Good point to check if anything else has stopped working - haven't noticed anything, but will check. Was impressed by how clean and bright all the connectors I have taken apart have been - the car is 19 years old, but they all looked brand new.

MK1 santa fe with 178k on clock...!

It has done its shift - cull it - the reason they sell new cars is old ones wear out!

 

[Islander71]

Well the good news is it isn't cutting out now, the bad news is it must be in full limp mode and will only rev to 2,700rpm! All electrics are working apart from the headlamp beam levelling which has never worked since I've owned it. Cannt think it will be the starter battery as the alternator would be charging when it cuts the engine. There are a multitude of wires and some connectors under the drivers seat, but bone dry.
Yes it is 178,000 miles, but was running very nicely until this problem - have seen one advertised with 250,000 miles, so they can do high miles. Just wish could find a basic car with no electronics, just mechanical injection.....

 

[dobbslc]

@premmington
Wash thy mouth out with used Castrol GTX!

157k a mere pup compared to the Santa Fe,



@Islander71 one of these ^ would be a good choice as they're fairly simple with minimal electronics and NO cambus nonsense.
I assume you have no ULEZ type cobblers up there so you'll be good to go.

 

[Islander71]

The trouble now with the likes of the Landcruiser is VED - I imagine it will be in the £760pa ? Local garage owner has been trying to sell me his one, but its an automatic which I dont like, or I would be tempted.
How long will a car run in limp mode? Might have to drive it to the ferry terminal, about 20 miles, then to the nearest breakers from Troon.
There is a LEZ in central Glasgow, but funnily enough my '91 Transit camper is classed a a classic and exempt, not that I would want to drive into Glasgow anyway....

 

[malcolm]

Out of interest I asked Grok AI for clues. It does mention running on as well as engine cutting out so likely the CAN bus is the problem.

Surprised it says that sensors or the fuel system can trigger a CAN fault but checking earths might be worth a shot. Might be worth clearing codes to allow checking battery voltage at high engine speed too in case the alternator isn't regulating - that could explain why it happens at 4000rpm. Are there any Hyundai specific forums where you can ask what the common causes are?

Here is what it said:

what are the common causes of fault code U0008 on a Santa Fe?




25 web pages
The U0008 fault code on a Hyundai Santa Fe indicates a High-Speed CAN Bus Malfunction, specifically related to high voltage or issues with the Controller Area Network (CAN) communication system. This code points to problems in the high-speed data bus that facilitates communication between the vehicle's electronic control modules. Below are the common causes of the U0008 code on a Hyundai Santa Fe, based on available information and diagnostic patterns:

1. Faulty or Damaged Wiring/Connectors in the CAN Bus:
   • Damaged, frayed, or corroded wiring in the CAN bus circuit can cause high voltage or signal disruptions, triggering the U0008 code.
   • Loose or poorly connected CAN bus connectors may lead to intermittent communication issues.

• Faulty ECU Relay:
  • A malfunctioning Engine Control Unit (ECU) relay can cause intermittent power supply issues to the engine control system, leading to CAN bus communication failures and symptoms like stalling or failure to start.

Issues with Sensors or Modules:

• Malfunctioning sensors, such as the crankshaft position sensor, camshaft position sensor, or EGR valve sensor, can disrupt CAN bus communication if their signals are erratic or their wiring is faulty.
• Problems with other control modules (e.g., 4WD module or ABS module) connected to the CAN bus may cause communication errors.
• Fuel System Issues:
  • A clogged fuel filter, failing fuel pump, or injector issues can lead to fuel starvation, which may indirectly cause the engine to stall or trigger CAN bus-related codes like U0008 due to associated electrical or sensor issues.
• Alternator or Voltage Regulator Problems:
  • A faulty alternator or voltage regulator may cause voltage spikes or inconsistent power supply to the CAN bus, resulting in high voltage errors.

Intermittent Electrical Issues:

• General electrical problems, such as poor grounding (bad earth connections) or short circuits in the CAN bus wiring, can cause the U0008 code. These issues may lead to symptoms like the engine cutting out or running on briefly after the key is turned off.

Symptoms Associated with U0008 on a Santa Fe​

• Engine stalling while driving (at high or low speeds) or at idle, often described as cutting out "as if switched off."
• Check engine light illuminated with U0008 code.
• Intermittent starting issues, where clearing the code temporarily resolves the problem.
• Power steering failure during stalling due to loss of power assist.
• Engine running on briefly after the key is turned off.

Diagnostic Steps​

1. Inspect Wiring and Connectors:
   • Check the CAN bus wiring and connectors for damage, corrosion, or loose connections. Focus on the engine control unit connector and diagnostic port.

• Test the ECU Relay:
  • Verify the ECU relay’s functionality, as a faulty relay can cause power supply issues.
• Check Sensors:
  • Inspect related sensors (e.g., crankshaft, camshaft, or accelerator pedal position sensor) and their wiring for faults.
• Examine the Alternator and Voltage:
  • Test the alternator and voltage regulator to ensure stable power output. Voltage spikes can disrupt CAN bus communication.
• Scan for Additional Codes:
  • Use an OBD-II scanner to check for other codes that may provide more context, as U0008 often accompanies other communication or sensor-related faults.
• Clean or Replace Fuel System Components:
  • If fuel delivery issues are suspected, inspect the fuel filter, pump, and injectors, though these are less directly tied to U0008.

Notes​

• The U0008 code has been reported in Santa Fe models, particularly older ones like the 2005 diesel model, with symptoms like stalling and intermittent starting issues.
• In some cases, clearing the U0008 code temporarily resolves the issue, but the problem may recur unless the root cause (e.g., wiring or relay) is addressed.
• Professional diagnosis with advanced Hyundai-specific tools is recommended, as CAN bus issues can be complex and require precise troubleshooting.

If you’re working on a specific model year or engine (e.g., 2005 2.2 CRDi), let me know, and I can tailor the advice further. For persistent issues, consider visiting a Hyundai service center with access to OEM diagnostic equipment.

 

[Islander71]

Thanks for replies. The AI result is interesting. Checked with the obd meter again now its gone into limp mode. It has come up with an extra code - U0003, High speed communications bus(+) open. Does this suggest a broken wire somewhere?

 

[malcolm]

Broken wire or bad connection somewhere or some fault in one of the other ECUs.

I would be checking the wiring under the driver floor carpet. All manufacturers put a connector under there which is guaranteed to get wet at some point and it's common to get a CAN fault. If you find a connector under there that has gone green it'll be a clue. But if it looks like the connector has got wet take loads of photos before pulling it apart as the wires can break in a corroded connector and you'll have no idea where they go without photos.

 

[OJCar]

Didn't someone on here end up breaking one of these due to an incurable CanBus issue?
(Think it was the gent that does Mazda rotaries but not sure).
If we can remember who that is, might be worth finding out what symptoms etc it showed.

 

[dobbslc]

The trouble now with the likes of the Landcruiser is VED

If you get a pre March 2001 car it's about £360 a year tax.