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Troubleshooting Idle Valve and Cold Start Injector error codes-ECU resistance to ground 700 1990

posted by  oldguy on  Sun Feb 13 23:01 CST 2011
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last visit: Mon Sep 1 13:35 CST 2014
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Had Cold Start Injector and Idle Valve error codes on my Regina 1970 740. Idle valve and injector resistance checks out fine. Opened and cleaned Idle valve and it seems to work fine (using 12v to fully open or 0 vlts close). Manual said to check harness wiring for proper grounding and resistance.

For Idle valve: harness it said there should be infinite resistance to ground on both sides of the harness. However the harness to ECU#33 is showing 73K ohms to ground, and the positive side is showing 85 ohms to ground.

Now according to the wiring diagrams the positive side of the idle valve harness is connected to the #9 ECU pin and also to the coil side of the radio suppression relay, which of course will have a resistance to ground of the relay coil resistance.

Is the ECU terminal #33 resistance of 73K ohms a good/normal value? Or if not is this a problem with the ECU?

For the regular injector harness to ECU terminal 18 is testing 10K ohms(all injectors disconnected from harness.)

Cold start injector harness to ECU 32 is 7 Meg Ohms to ground.

Injectors and Idle valve resistance is in spec.

Any knowledge if this is ok, bad ECU ?

Car runs typically without problems, but am fighting intermittent no starts, and I have connected an LED light across the injectors to trouble shoot injector(rule out), fuel, or ignition problem. Currently suspect intermittent coil or powers stage problem, or maybee ground. Have cleaned coil to powerstage but not yet tried.

Any help on what condition the ECU values to ground should be(key off).






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