Diagnostic Codes?!?

[J.T]

I've just done a fault code check on the GSi and have had the following codes come up
21. throttle position sensor - voltage high
38. oxygen sensor circuit - voltage high
56. idle air control - voltage high
73. mass air flow temperature - voltage low

What on earth do they mean in moron terms , do all the above need replacing or is one having a knock on effect??. The engine is fine for 20 secs then settles to 5-600 rpm where it misfires and sounds like my scooby does at 3-4000rpm, If i take the revs above 900rpm it becomes smooth again

 

[Neve'o]

1st off, check all the wiring to the sensors, including the connectors, thats alot of sensors to go wrong at once. if your happy the wiring is ok, then start off with a couple of second hand sensors for things idle air control, air mass, oxygen and throttle position, but id get a new oxygen sensor.

 

[J.T]

OH POOH!! The car has been stood for a year! I'll check that the condition of the wires is ok, i've just changed the crankshaft sensor as the outer sleeve was ripped. The previous owner thought the MAF was knackered before he laid it up for the past year, but thought it do a diagnostic to make sure. The ICV is clean but rattles, is that bad?

 

[oxbig1]

i had that same probs not that long ago. turnd out it was just the cam ans crank shaft sensors. lol. hole car was playiny up. it still has trouble starting when its cold. it gets sparks but i think its the fuel??

 

[Alex]

Check your earths as well mate, for that many sensor probs, there might be something else causing it.

Also might be worth testing your alternator as well

 

[J.T]

I'll have a good look at the earths tomorrow, as for the throttle switch, in the codes book the code related to a throttle potentiometer, is this a slightly more sophisticated switch or something else?.

 

[Alex]

It's a varing switch using resistance to indicate how far open said switch is

 

[IIIpythonIII]

deffo sounds like a whole heap of corroded wireing connections/bad earths,especialy after being stood

 

[J.T]

Its doin my nut in now!!!, all the earths are ok and the wiring all appears good, no corrosion at all on the plugs, changed the throttle sensor as found a spare throttle body in boot!! but still getting same code for that. Starting to wonder if the electrics are french

 

[oxbig1]

any walter went in the ecu? just popped in me head the now. well it has bn sittin 4 a while??

 

[mk3softtop]

id check the aultanator first b4 changing anything else it could be over charging

 

[J.T]

How do i check the alternator??
Is this a mad theory? one of the fault codes is that voltage is high on the mass air flow temp, is this the sensor before the MAF? If this is reading air temp incorrectly will that then make the lambda give a fault code, and then in turn cause the strange idle, so that the throttle and ICV think they are playing up, or am i talking pooh! (i am CRAP with wiggly amps and fuzzy logic

 

[16VSport]

Try cleaning up the sensors with carb cleaner, and the plugs and terminals with electrical contact cleaner, does the world of good. And take the car for a bloody good blast

 

[Guderian]

to me this points to a possible alternator issue (as others have said.)

check the output voltage is in the region of 14-14.5v with engine running, and approx 13.5v with engine running and headlights on. if its much higher then the regulator on the alt. is faulty.

for so many sensors to be logging high volts this is the most obvious cause. the one which is logging low volts is probably just a red herring..

 

[J.T]

Right will check the alternator and see what i get, cheers guys