ECU Fault Codes

[Matt Dunn]

We have a Link G4+ Extreme and have a couple of questions.

We have had the car apart and while assembling it it was run with some sensors unplugged, IAT, Oil temp etc.

Later when fully back together we had running problems.witn the engine.

When we connected PC link there were fault codes for saying something like

ANV 1 at 5V or similar.

I cleared them and they all went away and did not come back.

Question 1.

I thought that fault codes like that would self clear when the fault was rectified, i.e when the sensor was reconnected it would go away by itself. Does this not happen?

Question 2

Will the fault codes being in there cause running issues? One of them may have been the main ECT sensor, 

so will it affect the running? The car seemed to run better by just clearing the codes, or do we still need to look further for another issue?

[Dave Kriedeman]

Hi Matt, if you connect a PC to the ECU after you have had a fault, the fault will be displayed until the fault has been rectified and the fault cleared from the ECU. When there is a fault present such as an ECT or TPS input for example, the ECU looks at the set ERROR VALUE for that input and uses that value to help keep the engine running as well as possible until the problem is repaired, sometimes referred to as LIMP HOME STRATEGY or MODE. These values are fully user definable and are found under Analogue Inputs at the very bottom, under the Fault Settings Tab. I hope this helps, Regards Dave.

[Matt Dunn]

Thanks,

but the question is if I unplug the ECT sensor and then plug it back in while the car is running,

will it stay in limp home strategy even when reconnected, and need the Laptop connected to clear it,

or will it run as normal again as soon as the sensor is reconnected?

I know the fault will stay in the ecu but does it actually affect the cars running if it is a stored fault rather than a currently active fault?