Oil Pressure Fault

[Toddster900]

First post on this site so hi everyone and keep up the great work!

When accelerating hard with a cold engine my glow plug warning light starts to flash and the car goes into limp mode. Switching the ignition off and back on clears the warning light and the car runs fine again. Once its hot this does not happen.

Fault code P164B00 Oil Pressure Switch Mallfunction is activated following the fault. I did a bit of research and it appears there are two oil pressure switches. One located on the end of the block next to the air filter and one on the front of the block under the intake intercooler. As I was not sure which one was which or which one was causing the issue I shorted them one at a time with the engine stopped and the ignition on.

The one on the end of the block returned the code P164C00 Reduced Oil Pressure Switch Implausible Signal.

The one on the front of the block returned the code P164A00 Oil Pressure Switch Implausible Signal.

I then disconnected the one on the end of the block and started the engine which returned the code P164D00 Reduced Oil Pressure Switch Malfunction.

From this I am pretty confident my fault is being caused by the high pressure switch on the front of the block. I plan to change the switch but just wanted to see if anyone had seen these symptoms before and if anyone can explain why it only happens when cold. Could it be to do with cold oil reaching a higher pressure or a cold switch switching at a lower pressure?

Any input appreciated!

 

[OldVWFan]

I would not accelerate hard with a cold engine as this is hard on it due to oil being thicker. It sounds like when you accelerate hard when cold it causes a higher than normal oil pressure and this is not good so it puts the engine in limp mode. If your MFD shows oil temperature I would not accelerate high until this reached 180F of 82C and then see if you get the same fault codes. I never accelerate hard in my GTI until at least this minimum temperature.

 

[Toddster900]

Totally agree an engine should be allowed to warm up to be kind to it but it also shouldn't go into limp mode if accelerating when cold. There is a problem somewhere and ignoring it won't help.

As I said no faults once up to temp. I will take it out again in the morning to see what sort of engine speed causes fault and report back.

 

[OldVWFan]

You say it should not go into limp mode when cold and accelerating hard, but you don't know VW has programmed control module to handle this situation. It could this is to protect the engine and is not really a problem. Have you discussed this with dealer or good independent shop? Do you have an instrument like an OBD11 where you might be able to data log the oil pressure and temperature? This might give you some ideas as to whether it is a real problem or just inherent to the design.

 

[Toddster900]

If it was inherent it would have done it from new. Its a new fault that only started recently. The engine should easily be able to handle the type of acceleration I am talking about at any temperature.

Yeah I have OBDeleven and plan to investigate further tomorrow although I don't think oil pressure is available but I can monitor the switch state. The diagnosis window of the fault is very small as once the car is warm the problem doesn't exist so ran out of time today.

 

[jimlloyd40]

Seems easy to me. You said the car is fine and never goes into limp mode if it's properly warmed up. So don't do something you're not supposed to and the problem is solved. If you don't do something you're not supposed to because it's bad for engine parts (high acceleration - cold oil) it won't go into limp mode.

 

[Toddster900]

Not updated for a bit because I got distracted. Looks like there was a fault. After taking the switch plugs off to short them and work out which was which the fault has gone. I can only assume the high pressure switch had a bad connection and was never making which was causing the fault.

For future reference I have now had the car out whilst monitoring both switches and have observed the following.

The low pressure switch closes as soon as the engine is running and stays closed so long as the engine is running.

The high pressure switch closes a couple of seconds after the engine starts and then opens if left to idle. It then closes when ever there is an increased but sometimes minor load on the engine. This is the case when the engine is hot too and it runs like this without producing any fault codes so it looks like the high pressure switch should close during normal running.

Does anyone know under what conditions the high pressure switch should close and also under what conditions should it produce a P164B00 fault code?

 

[victorofhavoc]

I don't know the exact conditions but I know they're variable. They definitely change based on ambient and various engine/fluid temps.

The exact info you're looking for is tough to find outside of being friendly with a vw engineer.

You might just be chasing a ghost or characteristic here. If you're being intentionally hard on a cold engine it can definitely throw codes that will go away when restarted. It's like flooding your pcv and you get a misfire and missing cylinder. You restart the car and it's fine. The fault was just there to try to save the engine from falling apart on you in the assumption the conditions are "normal", but they're not.

 

[ROB_P95]

@Toddster900 did you get this sorted in the end? I have had a similar problem - it's under warranty but the dealer was hesitant to change anything as all the components passed the standard 'tests'. They cleaned up the connectors and the fault disappeared for 5-6 months, and it is now happening again. Oh and also, the acceleration doesn't have to be hard, just pulling away from lights as normal etc.