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Help Decipher These Fault Codes / Live Data Spi


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#1 minisilverbullet

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Posted 12 July 2014 - 05:21 PM

So... The story goes....the car has had a fluttering idle speed, it is an intermittent issue. Sometimes, not at all sometimes mildly, sometimes a bit worse. At its worst it can fluctuate between 900rpm to almost staling.

I have a code reader with the rover 2 pod.

The ecu had 2 fault codes -
16.throttle pot circuit fault
2. Inlet air temp sensor CCT fault.

I was able to clear the air temp fault. Though I couldn't clear the other. The air temp fault came back after a drive. So I know I have two pressing faults

Live data at idle

Engine speed - 904
Throttle pot - 0.30v
Map sensor - fluctuated between 031- 036 kpa
Inlet temp 35, this has never altered, I have used the code reader a handful of times
Lambda - 0.8v


Live date at 2000rpm

Throttle pot - 0.90v rising to 1.06
Map - 028
Inlet air 35
Lambda 1.2v

Any pointers.....

#2 minisilverbullet

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Posted 12 July 2014 - 05:40 PM

Throttle switch is also always open, event at idle, not sure if that's normal

#3 RedRuby

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Posted 12 July 2014 - 06:25 PM

I am by no means an expert as I am learning my code reader as well, but, the map sensor at idle should give a nominal reading of about 30Kpa so yours are I would think within limits. The Inlet temp at 35 and lambda at 0.8 would suggest that your ECU is in limp home mode due to a fault, probably the inlet air temp sensor and the potentiometer which should have a range between 0.5 and 4 volts.

Do you have a manual for your code reader, if not and it is an ACR 2 or 4 PM me with details and an e-mail address and I will be able to sent you a copy of mine.

#4 FlyingScot

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Posted 12 July 2014 - 06:35 PM

For an SPi you should use Rover Pod 1 not 2 but in practice it seems to make little difference.

Check the wiring to the two sensors first before condemning them.

Is your car fitted with a throttle switch? The code reader will report it even if not physically present but some SPI models do have the switch.

Easy way to check MAP is test with motor not running but ignition on (should be 100kpa then around what you have found when running).

The throttle pot is best checked with a multimeter and in the first instance you are looking for a smooth change in resistance (any jumpiness means its worn out) or check the voltage as per RedRuby again a smooth change in reading if what you are looking for.

Also check you have a voltage being supplied to the throttle pot, I just had one where there was no voltage present and it reported the fault.

The live lambda reading should be changing rapidly up and down, if its stuck at 0.8 then you have a fault.

Like RedRuby I suspect with the two readings you have quoted it is in limp home.

 

FS



#5 minisilverbullet

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Posted 12 July 2014 - 07:02 PM

By chance I had a spare air temp sensor and tps, I have just changed these over! And no change on the air temp. I have the Manuel (thanks for the offer though).

The tps behaves a strangly, starts of at around 0.20 then steadily rises to 0.80 at idle, I can see the stepper motor pushing on the linkage. Sometimes it raises smoothly with throttle other times it doesn't adjust at all.

I tried moving just the tab on the tps without moving the throttle the value did rise but only to around 1.8.

guess this could be a wiring fault?



Lambda value adjusts.

#6 xrocketengineer

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Posted 13 July 2014 - 01:41 AM

Throttle switch is also always open, event at idle, not sure if that's normal

My understanding is that early SPI engine with two connectors on the ECU had the switch. The later ones had no switch but the switch state is calculated based on the TPS readings.

I had a TPS problem on 2002 Hyundai.  With a fixed throttle pedal position the speed of the car would increase gradually as the TPS voltage would also change. Using an Ohmmeter, the resistance of the TPS would not increase/decrease linearly. It would randomly changed values with the throttle valve opening. 

 

From the Rover Technical Bulletins:

Throttle potentiometer sensor
(TPS)
A TPS is provided to inform the ECM of rate
of acceleration. The TPS is a potentiometer
with three wires. A 5.0-volt reference voltage
is supplied to a resistance track, with the
other end connected to earth. The third wire is
connected to an arm which wipes along the
resistance track, and so varies the resistance
and voltage of the signal returned to the ECM.
From the voltage returned, the ECM is able
to calculate just how quickly the throttle is
opened. From model year 1993 onwards, the
TPS also informs the ECM of idle position with
a voltage of approximately 0.6 volts.

 

Throttle pedal switch
Until the 1993 model year, the throttle pedal
switch indicated a closed throttle to the ECM.
The ECM was then able to recognise the idle
speed condition and also deceleration. From
1993 models year, MEMS recognised the
closed throttle condition with reference to the
TPS signal.



#7 minisilverbullet

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Posted 14 July 2014 - 07:45 PM

TPS
I have test the tps sensors ( I have 2). Using a multi meter as advised above I got a smooth reducing resistance when moving the arm. Same readings on both. So I know I have 2 working tps.

I also checked that I have a 5v supply at the tps, I do.

Now with the engine running the voltage of the tps using the code reader begins at 0.20 and gradually rises to 1.5 after around 5 minutes using the code reader.

Another oddity with the tps, there is no change at all on the code reader when I raise the rpm. I also tried just moving the arm/pin on the tps, and it did nothing; didn't effect the running of the car nor effect the reading on the code reader.

INLET AIR

Off the car, I also have 2 sensors, both behave the same in terms of resistance starting high and lowering when I heat the sensor up, so these are also good.

I am not sure how to test the actual wire the sensor connects to! But what I know is there is no voltage through either of the wires. When I place the multimeter over the 2 using the resistance setting there is a steady resistance figure. Not sure if these are normal.

I also started the car with both the air temp and throttle position removed and it ran exactly how it has been. So I am sure the above are the issues.

I also stripped back all the wiring tape/ wrap etc and the wires appear fine!

Any ideas.....,

#8 dbcool20

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Posted 14 July 2014 - 09:06 PM

With the ignition turned ON, if you remove the air temp sensor and plug your multimeter in the 2 pins of the connector you should deffinitely get a voltage. Don't remember what it should be, (maybe something like 5v) but you should get a voltage. If not maybe you have a broken wire. But remember to measure the value with the ignition turned ON otherwise its normal you have 0 volts.



#9 minisilverbullet

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Posted 14 July 2014 - 09:25 PM

With the ignition turned ON, if you remove the air temp sensor and plug your multimeter in the 2 pins of the connector you should deffinitely get a voltage. Don't remember what it should be, (maybe something like 5v) but you should get a voltage. If not maybe you have a broken wire. But remember to measure the value with the ignition turned ON otherwise its normal you have 0 volts.


Many thanks! I have no volts, I guess I check the wiring again.

#10 xrocketengineer

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Posted 14 July 2014 - 09:59 PM

Ok, looking for common things, pin 30 (pink/black wire) of the ECU seems to be the the 5VDC source. It powers, with the same colour wire, the IAT, the TPS and the CTS. It also provides 5VDC to one of the pins of the diagnostic socket with the same wire colour.

I believe that you have already verified 5VDC at the TPS with a voltmeter and the ACR is talking to the ECU indicating voltage at the diagnostic pin.

So, what is left that is common is the ECU connector for the the failed sensor indications. I would disconnect the ECU connector, inspect it and attempt to clean the contacts by connecting and disconnecting the connector several times. If that solves the problem, try some dielectric grease to protect the ECU connections like:

http://www.permatex....p-grease-detail

 

PS you found no voltage at the IAT while I was typing. It appears that you have a break on the pink/black wire.


Edited by xrocketengineer, 14 July 2014 - 10:02 PM.


#11 minisilverbullet

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Posted 14 July 2014 - 10:11 PM

Great, getting closer! I will check the wiring again tomorrow, I think it is a pink wire with a thin black stripe.

Coolant temp is fine!

I wonder if the limp home mode induced by the iat, over rides the tps?

#12 xrocketengineer

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Posted 14 July 2014 - 10:21 PM

From the Rover Technical Bulletins:

 

LOS (limp-home mode)
MEMS has a limited operating strategy
(LOS)or limp-home facility, and in the event of
a serious fault in one or more of the sensors,
the EMS will substitute a fixed default value in
place of the defective sensor.
For example, in limp-home mode the
coolant temperature sensor (CTS)value is set
to 60°C, the ATS is set to 35°C, and engine
load is based on rpm. The engine may
actually run quite well with failure of one or
more minor sensors. However, since the
substituted values are those of a hot engine,
cold starting and running during the warm-up
period are likely to be less than satisfactory.
Also, failure of a major sensor, ie the MAP
sensor, will lead to a considerable reduction in
performance.

 

Maybe the TPS is ignored?



#13 dbcool20

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Posted 15 July 2014 - 09:18 AM

Another easy way of checking the IAT connector is as you know one of the two wires is a 5v and the other is a ground, so if you connect one lead of your voltmeter to a good ground, i.e. the thick grounding strap that goes from the block to the frame, and then with the other lead of the voltmeter you try the 2 pins of the connector you should now get a voltage on one of them. If you get a voltage this way it means you have a problem with the ground wire of the connector. and if you still find 0v on both pins by doing this then its most likely your 5v feed wire is the problem. By doing this you can identify which wire is the problem, then once you know if its the + or the ground (or Both) i would try first visually inspecting the line, and if you don't see any cut or damage then remove the ecu connector as said above and have a look at the pins like xrocketengineer said. If you have a wiring diagram or if you know which pins are what on the ecu connector for the IAT i would then try measuring both lines from the ECU connector to the IAT plug with an Ohm meter, this way you will also see if you have a broken wire.

 

Cheers 



#14 minisilverbullet

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Posted 15 July 2014 - 08:23 PM

Thanks guys for the advice thus far.

So I have traced the iat all the way back. The pink black wire leads to a 5 way soldered connection. All 5 are pink/black, 1 leads to the ecu, one to the iat, one to the tps and one to the diagnostic socket, the 5th I am not sure.

Measuring the voltage of these wires: at the connection, at the tps, at the iat and at the diagnostic pin. All read 0.3v

There is continuity on all of the above so no breaks.

The other wire in the iat sensor, I traced back to the ecu and then checked it with the continuity setting on my multimeter, again no breaks. No voltage on this wire, I guess this is normal since the sensor must work as a resister.

Back to the tps. I think I mentioned above I had 5v at the tps. I do but not on the pink/black wire, which reads 0.3v. The third pin reads 0v.

I guess I should be getting more than 0.3v on the pink/black wire?

#15 xrocketengineer

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Posted 15 July 2014 - 09:21 PM

Ok, from what I can tell from the wiring diagrams, the TPS should have three wires. Pink/black from pin 30 of the ECU that should be 5 VDC supply, yellow/green that is the variable resistor wiper and goes to pin 8 of the ECU and yellow/purple that should be the earth reference from the ECU pin 9.


Edited by xrocketengineer, 15 July 2014 - 09:31 PM.





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