Fault Codes P0420, P0116, P0203, P1327

Hi All,
I haven't been on this site for some time as the C3 has been running great and is still running great apart from a few recent hiccups.
The first problem occurred mid summer when returning from a day trip, the temperature gauge suddenly shot up from two bars to the red. I stopped the car and it definitely wasn't over heating. I got home, switched the engine off and the fan kept running, so rebooted the computer and all was fine until stuck in traffic, a couple of weeks ago when it did the same again, a reset did the trick again. If I do need to change a sensor, would that mean changing the one that goes to the temperature gauge or the one that goes to the ECU?

About a week ago driving to the work the EML came on, there was no problem driving it, but when I got the lexia onto it it came up with a P0420 Cat ageing code, I cleared that code and also one that was related to the temperature gauge I think P0116 Coolent Temp sensor signal coherence. All fine again until last Friday when stuck in traffic and the EML came on and the engine felt like it was running on three cylinders and kept cutting out. After a few restarts the light went out and it has been running fine ever since. Yesterday checked the codes again and got codes P0203 injector control, P1327 Injector of phase interrogated with ignition, P0420 Cat ageing and also not a code but said something like, No Permanent Positive of Time Display. There was also the P0116 code again. I am not sure if the temperature gauge issue is separate, but also read somewhere that if there was an issue with the Cat or o2 sensors the engine might shut down an injector to protect the Cat.
I don't really want to start replacing everything if all the codes were related to one issue any help would be appreciated. The car is a 1.4 2003 16v. Thank you

Hi Outbound1

As soon as codes that seem unrelated but arise from the same area, ie under the bonnet, start to crop up I always look for possible common links.

In this case all you faults could be down to battery voltage or the battery supply. I would start out by checking your battery, cleaning the terminals and checking the earth straps, especially to the engine block.

Many sensors work by measuring resistance, a poor earth or low supply voltage will give false readings.

This could be totally unrelated, but still worth doing anyway and it eliminates electrical supply problems which can generate spurious codes by the bucket load!

I would then clear all your codes and go from there.

Hi Missing Lincs,
Thanks for your reply. Funny you should mention the battery. One other problem I have had which had happened a few times within the year was that the car would just cut out perhaps once every couple of months or so. there were no codes and it would start straight up with no other problems. When I went to disconnect the battery from something a couple of month's ago I noticed a lot of, I don't know quite what you would call it, but a great pile of grey powder around the battery terminal as if it had been sparking. It had got so bad that the original battery clip had got damaged beyond repair and i couldn't get a decent replacement, so I bought a good heavy duty bold on battery clip. I thought that this was causing the car to cut out due to sparking due to the bad connection. When I have disconnected the battery over the last week I have noticed that although the bolt on connect is tight the grey powder is returning. Which you reply has now made me think what could be causing the build up of the grey powder.
Thanks once again, Jeff

Sorry forgot to mention that the car according to the Lexia is charging at 14.5 volts.

Just been out to look at the battery. The clamp is still tight, but there is loads of the blue/ grey powder around the positive terminal.

Outbound1 wrote:Just been out to look at the battery. The clamp is still tight, but there is loads of the blue/ grey powder around the positive terminal.

There are some battery terminal clearing tools (here) on Amazon that are cheap enough and can clean that corrosion off to leave a better electrical connection.

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and when they have a nice metal to metal contact, protect them with a smear of this battery terminal gel (here) to keep them good.

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Thanks C3driver52,
I managed to give the terminals a good clean today, one cell in the battery was half empty. I used petroleum jelly for now but will get some of what you posted.
Thanks for your advice, Jeff