Grant Scoones

An update on the A3. After installing the replacement oil pump the remaining job was to have the oil pressure tested using a gauge by my local Mitsubishi service agent. At the same time, I purchased a new OE Oil Pressure Sender and had them fit that too as they had to remove the old one to fit the oil pressure meter. The pressure test confirmed that oil pressure was within the correct operating parameters, and pointed to the sender unit being the cause of the Low Oil Pressure warning. The new OE sender was installed, and surprise, surprise, the LOP warning light was gone. So, a few dollars spent for peace of mind. I have a suspicion that the cause of the low pressure warning was probably a broken earth wire on the original Oil Pressure Sender, which was then replaced by an aftermarket sender that did not not include an earth wire, so unsurprisingly, the previous owner continued to have the LOP warning. The replacement VAG OE Sender Unit I purchased (NZ$76) included a new earth wire and my workshop duly earthed that to the engine via one of the Oil Filter housing mounting bolts. Problem solved. Buying the A3 with LOP warning was a risk, but the engine always sounded smooth and quiet, so a risk worth taking. The car has now doubled in value, but I think I'll hang on to it for a while as it has only done 117,000km and is in unmarked, original condition. Yeeha.... 🙂

Further gentle testing of the engine after fitting the oil pump reveals that the Low Pressure Warning Light comes on @1500 rpm, which I understand is the "trigger" revs for the switch itself. Once the light comes on, it stays on until the ignition is turned off, then the light will not come on again after restarting the engine until 1500 rpm is reached. I agree with you that the sender unit is likely the cause, but will have a chat with Audi Service Agent today to see if that code should come up using the authentic VAG Scan tool (VCDS?). Sender units are cheap enough, even the OE version, so I may just start stripping stuff off the front of the engine to allow me to remove the sender. Taking the car to the Audi Dealer 30km away is an option, but they charge like wounded bulls, so will try and avoid that. 🙂

Thanks Cliff. Audi did some wonderful design work mounting the oil pressure sensor on the side of the oil filter housing, but buried deep within the plumbing and accessories at the front of the engine. A deep, large socket is required to loosen the sender but typically, it's nigh on impossible to get a socket wrench into the limited space available. Audi may know of a shortcut for this, but the workshop manuals I have fail to mention how this is done. Our Audi agent is 30km away and while the engine runs quietly and smoothly, even with the low oil pressure light glowing, it would still be a risk to drive it there, so I'll probably use our local Mitsubishi service centre. I still have no idea why the trouble code doesn't show up on the OBD2 scanner.

Progress so far. Referring to The Haynes Manual and on online A3 workshop manual, I was able to remove the oil pump balance shaft assembly, although working underneath the car was a little difficult at times. Oil pump stripped and checked for impeller wear all okay. Balance shafts running smoothly on their bushes with no obvious wear but I decided to fit the lower km unit I'd bought anyway. Decided to change the oil filter and had a hell of a job removing the cannister to access the cartridge as it appeared to have been over considerably overtightened by the previous service agent. Tried a 36mm steel adaptor, but !Removed! it had rounded edges and the cannister was so tight, it kept slipping on the 36mm plastic hex. Finally purchased a heavy duty 36mm steel socket and with the use of a rubber mallet, eventually got the cannister unscrewed. Inside of the cannister was clean as was the filter. replaced the filter and tightened cannister to correct torque setting! Carefully assembled and refitted all parts, including using sealant on mating surface of the oil pump balance shaft unit intermediate plate engine block surface, per manuals. Added new engine oil and turned the motor over with sparks plugs out to circulate oil and prime the oil pump. Refitted the plugs, turbo pipes, air cleaner/engine cover and after a careful check, started the engine. Engine burst into life and ran smoothly straight away. Not nasty noises etc that could indicate low oil pressure. Idled engine for a few minutes checking for oil leaks (all good) and then blipped the throttle a few times up to around 3500. Initially okay, then the Low Oil Pressure warning sounded and the light came on the dash. Engine still sounded quiet. So, after a week of work and replacing the pump, I'm still at square one, although I'm now fairly sure the engine oil pressure is probably okay. What I'm less sure about is the Oil Pressure Sensor, which the previous owner had replaced by a service agent in NZ. The invoice for that service confirms the sensor was replaced, but now I'm not so sure. It wasn't done by an Audi Dealer and there is no indication of a bright, shiny new pressure sensor, which I would expect, bearing in mind that the car wasn't used after that service because of the oil Pressure Warning light. I've scanned the ECU with my OBD2 device and no trouble codes are present, which I would expect if there was a low oil pressure warning. It's not the VAG Diagnostic Tool, so will probably get a scan done by Audi and also have the oil pressure checked on a meter. Other than that, I'm not sure what else I can do. Any thoughts?

Thanks for your input Clifford. The low oil pressure warning light first came on in September 2021. The light would only trigger above 2,000 rpm. The motor was running quietly and smoothly at the time and continued to do so up unil I bought it. The owner took it for a service to have it checked out. Oil and filter were changed and a new oil pressure switch and oil cap fitted. The low pressure warning continued to show and the service centre diagnosed a faulty oil pump. The owner then garaged the car until I bought it recently. Engine started smoothly from cold and drove just fine, but the low pressure light continued to come on. I purchased the car and had it trailered home to do the pump change. Local VAG agent quoted me NZ$9,000 to replace the pump with $5k of that being parts, $4k labour!!!, so that was ruled out. Replacing the pump myself without removing the engine was the option I chose, which is where I am now. I have sourced a replacement pump for $350 and have removed the oil pan but the oil pump drive chain is preventing me from lowering the pump from the block. The checklist you sent me was helpful, but I've done all of that, as had the previous owner. Not sure about there being an oil pressure relief valve, but will check that out for sure. The car has a filter element rather than the screw on type filter.

Hi from New Zealand I have a 2005 A3 2.0 TFSI S Line with 117km on the clock. The low oil pressure warning has been showing when the engine is revved beyond 2,000 rpm and the diagnosis is faulty oil pressure pump. The oil pressure sender has been changed, eliminating that as a source of the problem. I have sourced another oil pump and have dropped the oil pan to access the pump, but taking out the pump balance shaft assembly appears impossible without taking off the drive chain and I can't do this it seems without taking the chain off the oil pump sprocket. A search of youtube, google etc hasn't been that helpful and I would appreciate any advice on "where to now"?". Thanks in advance.