No Start: Audi 100, 1990, I5 NF engine, non-turbo, non-quattro, CIS-E-111 (California)

Marc Boucher mboucher70 at
Thu Sep 1 20:18:03 PDT 2011

At this point, I've located a replacement ICU for a reasonable price.  I 
also believe that I've exhausted all reasonable tests that would point to it 
being something other than the ECU (ICU/Fuel-Injection CU combination).  So 
I'll probably order it.  Just wanted to first detail the additional tests 
that I've conducted, and information that I've gathered, and see if there 
were any final tests anyone has to recommend.

All three wires from hall sender to ICU were measured, once again, for 
resistance.  This time on the Rx1 scale.  There is no measureable resistance 
in any of these wires between the plug in the engine bay that connects to 
the hall sender and the plug that connects to the ICU.

Previously, I'd measured the voltage between the red/black wire and the 
brown/white wire of the hall sender, and got the expected 12 volts with the 
ignition on.  But then it occurred to to check the voltage between the 
red/black wire and the the car's ground...this is also 12 volts with the 
ignition on.  So then whats's the resistance between the brown wire and the 
car's ground with the ignition on?  Its circuit.  How can 
red be 12 volts to both the car's ground and 12 volts to the brown wire, but 
the brown wire has no connection to the car's ground?

Next I put the multiimeter between the car's ground and the hall sender's 
brown wire and cranked the engine.  It read about 5 volts.  Then I switched 
to a current scale which would allow current to pass and hence the car to 
start.  Car started, but I couldn't read the current, likely because its 
switched, not DC.

Just to be complete, here's a list of additional actions that I've taken:

Remove the ground wires attached to the intake manifold and test for 
continuity with ground at the ICU.  Even though it was good, I nonetheless 
cleaned the ring connectors and reattached them with a bit of dielectric 

Checked the continuity of every wire between the ICU and the fuel injection 
control unit !!!

Previously all grounds were checked successfully, but you'd raised the 
possibility of a wire showing a good connection using an ohmmeter but not 
being able to carry a sufficient current.  To eliminate this possibility I 
ran a second, parallel ground to each of the ICU and Fuel Injection unit's 
ground terminals.

Any last tests that anyone care to recommend before I get the replacement 

If I do order the replacement ICU, any other parts that I should probably 
pick up while I'm at it?  Not specifically for this problem, but since I 
plan on keeping this car a few more years, and since shipping parts 1 by 1 
gets pricey, I may as well stock up on a few things if I place the ICU order 
from Force 5, that needs to ship it.

Thanks again


ps: on a side note, the same week that the car died, my giant plasma tv 
died.  Everyone told me it wouldn't be possible or economical to fix. 
Tonight the board I believed to be at fault arrived, at a low ebay price, 
and now its repaired and working.  Surprised that I was able to get that 
working sooner than the car, since the electronics are far more basic in the 
car....that's just how it worked out.  TV is done, car is next.

From: "Huw Powell" <audi at>
Sent: Wednesday, August 31, 2011 12:03 PM
To: "Marc Boucher" <mboucher70 at>
Cc: <quattro at>; "Tony Hoffman" <auditony at>
Subject: Re: No Start: Audi 100, 1990, I5 NF engine, non-turbo, non-quattro, 
CIS-E-111 (California)

> see below
> On 8/31/2011 12:14 AM, Marc Boucher wrote:
>> Tonight I did some tests of the Hall Sensor and connection from the
>> sjmautotechnik link.Here are the tests and the results.
>> “Remove the three terminal connector from the distributor for the hall
>> effect sensor, using a DMM check for ~12VDC, (at least 9 Volts) between
>> terminals 1 (Red/Black wire) and 3 (Brown/Red), the two outer connector
>> pins with the ignition key on. Pin 1 is the first terminal on the left
>> with the spring release clip wire towards the top. The 10V Engine ECU
>> supplies ~+12V to this hall effect connector at pins 1 and 3. “
>> _Result:_12V measured between red/black wire and brown/red wire.PASS
>> “Use a DMM and check for low (<1.0 ohm) resistance between pin 1 and
>> engine ground, in one case, resistance between this terminal and the ECU
>> caused a no start condition, even though 12V was measured across pins 1
>> and 3.”
>> _Result:_Resistance between red/black wire (terminal 1 of wire to hall
>> sender) and ground measured approximately 100 ohms !! (It measured 100
>> ohms in 1 one direction and about 150 ohms when the leads of the ohm
>> meter were switched around)
>> _Further Result:_Note that terminal 1 of wire to hall sender connects to
>> PIN 4 of the ICU.I unplugged the wire harness going to the ICU and
>> measured the resistance between PIN 4 and the other pins which are
>> grounded (20 and 22).I got the identical 100 ohms / (150 in other
>> direction) between PIN 4 and PIN 20 (which is grounded when plugged in).
>> _Question: _
>> 1.)The red/black wire to the hall sender is the positive terminal when
>> the ignition is energized.Why would the positive terminal measure < 1
>> ohm when the ignition is closed?
> I don't know - I think there is an error there.  SJM is telling you to 
> make sure the ground at the sender is actually good, so perhaps he meant 
> pin 3?  Keep in mind his site isn't about your engine, it's about the 
> turbo systems only, I think.
>> 2.)Assuming the test is correct, then the ICU should have < 1 ohm
>> between PIN 4 and ground, but since it has about 100 ohms, and since all
>> the grounds check out on the ICU, is this a clear indication that the
>> ICU is bad?
> No, it could be a bad connection or wire too, I think.
>> 3.)If the car starts when the brown wire from the hall sender is ground
>> (the temporary fix that the garage put in), does this rule the
>> possibility that the hall sender is bad?
> If the engine runs in any way at all, on all 5 cylinders, the Hall sender 
> *must* be working.
>> *From:* mboucher70 at <mailto:mboucher70 at>
>> *Sent:* Sunday, August 28, 2011 1:13 PM
>> *To:* quattro at <mailto:quattro at>
>> *Subject:* No Start: Audi 100, 1990, I5 NF engine, non-turbo,
>> non-quattro, CIS-E-111 (California)
>> I've updated the list below with some additional tests and two minor
>> corrections in what I'd typed before.
>> _Additional tests:_
>> Disconnected hall generator and verified continuity of each of 3 wires
>> to ECU:
>> Red-Black to PIN 4 on Ignition Control Unit : PASS
>> Brown-White to PIN 10 on Ignition Control Unit: PASS
>> Green-White to PIN 24 on Ignition Control Unit: PASS
>> Also performed this test in a 'duplicate' manner by running a second
>> wire from the brown-white to PIN 10. Still, no start.
>> _Additional or Repeated Ground Tests:_
>> Re-verified that the ground PINS for the Fuel Injection and Ignition
>> Control Unit listed below are all ground. All Pass.
>> In addition, performed a physical inspection of the ground points.
>> Engine ground behind intake manifold
>> Engine ground linking ignition to rocker cover
>> Main engine ground
>> The only ground that I can't find is described as "a brown wire that
>> attaches to the base of the right side of the "A" pillar. This grounds
>> Pin 22 on the Ignition Control Unit. PIN 22 measures that its connected
>> to ground, but I'd still like to find the actual connection and verify
>> it. The base of the right-side "A" pillar is where the Fuel Injection
>> Control unit is located. I can't find any brown wires attached to the A
>> pillar anywhere around there. Anyone have any ideas on how to find this
>> final ground wire? I did find a major ground attached to the left
>> (driver's side) A pillar almost at the level of the bottom of the
>> driver's window. This seemed like it was a ground for the dash. But I
>> can't find a ground wire on the right side A pillar.
>> _*Further Tests or Conclusions:*_
>> 1.) At this point, the grounds to the Ignition Control Unit and Fuel
>> Injection Control Unit have been checked and rechecked. We know the
>> Ignition Control Unit is grounded. We know that the car starts when the
>> brown-white wire on the Hall Generator is grounded. We know that the
>> brown-white wire on the hall generator has continuity with PIN 10 on the
>> Ignition Control Unit as per the schematics. Thus isn't it a reasonable
>> assumption at this point that the ECU system is grounded, and its simply
>> not passing the switched ground onto the Hall Generator or, for that
>> matter, all the other items that it controls (since ISV,
>> Carbon-Canister, Cold-Start, and differential pressure regulator all
>> failed tests)? IE, isn't it a reasonable conclusion that the fault is
>> indeed in the ECU, and not the wiring?
>> 2.) If the car starts and drives well using the hall ground that the
>> mechanic installed, is there any risk in driving it short distances
>> until I get a new ECU, or get the problem fixed? In other words, I
>> understand that the ECU (combined Ignition Control Unit and Fuel
>> Injection Control Unit) serves the primary purpose of optimizing
>> performance by adjusting ignition and fuel across a wide range of
>> temperatures, pressures, etc.. Without it, the car won't shut down, its
>> simply going to run rich or lean or idle too fast or slow. Is this 
>> correct?
>> Thanks again,
>> MC
>> ------------------------------------------------------------------------
>> As Suggested by Huw, here is the recap of the problem and the tests
>> performed so far:
>> _Car: Audi 100, 1990, I5 NF engine, non-turbo, non-quattro, CIS-E-111
>> (California)
>> _
>> __
>> _Problem:_ Car cranks but won't start.
>> _History:_ Car was driving, and suddenly shut off, unable to restart.
>> Towed to nearest garage which (correctly) noted no spark and
>> (questionably) "solved" the problem by splicing the brown-white wire
>> leading from the hall sender to the Ignition Control Unit, and grounding
>> it to the engine block. This drove fine, but I noticed car was idling
>> faster than before, ISV not working. Based on comments in this mailing
>> list, and the simple fact the repair was not correct, I've set off to
>> find the real problem, and correct solution.
>> _First step, remove the ground wire that the garage added to the hall
>> sender, thus restoring the previous no-start condition. After this:
>> _*_Tests Conducted So Far:
>> _*
>> *__*
>> _All fuses verified.
>> _
>> _Throttle switch testing performed as precursor to ECU output tests.
>> _Result: Resistance between pin 1 and 2 when throttle closed = 0.2 ohms
>> Resistance between pin 1 and 2 when throttle opened = infinite
>> Resistance between pin 2 and 3 when Wide Open Throttle = 0.2 ohms
>> Resistance between pin 2 and 3 when NOT Wide Open Throttle = infinite
>> Conclusion:
>> Throttle switches functioning. Can proceed to ECU Output tests.
>> _ECU Output Tests Results:
>> _ ECU is sending 100mA to Differential Pressure Regulator, regardless of
>> state of throttle body. FAIL.
>> ECU is cycling carbon canister solenoid valve on and off, regardless of
>> state of throttle switch. FAIL.
>> ECU does not activate Idle Stabilizer Valve, regardless of state of
>> throttle switch. FAIL.
>> ECU activates Idle Cold Start Valve, cycling it on and off for 10
>> seconds, regardless of state of throttle body. FAIL.
>> _ECU Fault Code Listing:
>> _After cranking engine for about 7 seconds, the codes that came off were
>> 4444-no codes recorded
>> 4444-no codes recorded
>> 0000-end of diagnostic output
>> 2122-Engine speed sensor signal missing, signal used by Ignition Control
>> Unit
>> 0000-end of diagnostic output
>> _Wiring tests of Ignition Control Unit:
>> _Unplugged the Ignition Control Unit and verified via ohmmeter the
>> following connections:
>> Ground to PIN 22 in ICU cable. PASS. Connection good.
>> Ground to PIN 20 in ICU cable. PASS. Connection good.
>> Tony had mentioned a 3rd ground wire to the Ignition Control unit, but I
>> could only find two PINS that should be ground on the schematics.
>> Connection from brown-white cable of hall sender (which had previously
>> been spliced) to PIN 10 of ICU. PASS. Connection good.
>> _Wiring tests of Fuel Injection Control Unit:
>> _Unplugged the Fuel Injection Control Unit and Verified via ohmmeter
>> both ground connections:
>> Ground to PIN 35 in Fuel Injection Control Unit cable. PASS. Connection
>> good.
>> Ground to PIN 18 in Fuel Injection Control Unit cable. PASS. Connection
>> good.
>> Tony had mentioned a 3rd ground wire to the Fuel Injection Control Unit,
>> but I could only find two PINS that should be ground on the schematics.
>> _Additional Notes:_
>> Both the Ignition Control Unit and the Fuel Injection Control Unit were
>> properly installed inside elastically closed plastic bags. The terminals
>> (the plugs) of each unit were shiny with no hint of corrosion. I noted
>> just a spec of something in one of the sockets of one of the plugs and
>> on further examination it was some type of grease. Point is that I
>> believe that these units were cared for in terms of ensuring they didn't
>> get wet, corrode, and that the electrical contacts were not degraded (at
>> least inside the car).
>> Thanks Again to all for any suggestions as to what I could test or try 
>> next.
>> MC
>> ------------------------------------------------------------------------
>> No virus found in this message.
>> Checked by AVG - <>
>> Version: 10.0.1392 / Virus Database: 1520/3868 - Release Date: 08/30/11

More information about the quattro mailing list