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How to interpret Focus 9 DME diagnosic lights
Posted: Wed Jan 21, 2026 6:56 am
by chrischrischris
I'm working to resolve a no-start/hard-start issue on my 87 turbo that came out of nowhere. I have the Focus 9 DME relay with the four diagnostic lights installed and I want to make use of the information they provide. But, it's not obvious to me how to do that.
If I suspect that I have a faulty alarm module that is preventing the car from starting, what would I see?
Would any of these lights illuminate?
Ignition SW – (Yellow) Input signal to power up fuel injection system and enable fuel pump control.
Fuel Inj. Power – (Red) Output indicating the fuel injection system is powered up.
Ctl. Fuel Pump – (Blue) Input signal indicating the DME has commanded the fuel pump on.
Fuel Pump – (Green) Output indicating the fuel pump is powered up.
Re: How to interpret Focus 9 DME diagnosic lights
Posted: Wed Jan 21, 2026 8:38 am
by walfreyydo
Here is the DME relay diagram:
https://www.clarks-garage.com/shop-manual/fuel-05.htm
Each of the lights on the DME relay corresponds with an output on the diagram. Fuel Pump light references power to the 87B, Ignition SW = port 86, Fuel Inj Power = 87, and (I assume) Ctl. Fuel Pump is verifying that DME is providing a ground for the pump = port 85B.
Your question pertains to the alarm and if when the alarm is active what light would be affected. As per the guide on Clarks (
https://www.clarks-garage.com/shop-manual/fuel-16.htm) the alarm disables the power going to port 86 (ignition switch), so if that light is not coming on on your relay:
the ignition switch is bad, there is a problem with the alarm system (if equipped), or there is a broken wire between the battery and ignition switch, between the ignition switch and alarm module (if equipped), or between the alarm module and fuel pump / DME relay. If equipped with an alarm system, bypass the alarm system using
ELECT-23, and repeat the test.
If you are trying to troubleshoot a no start condition, I would recommend you read through and follow the guide here:
https://www.clarks-garage.com/shop-manual/ts-01.htm
A good starting point is to check your fuel pressure (it must be with a gauge) and verify if its
within spec.
Re: How to interpret Focus 9 DME diagnosic lights
Posted: Wed Jan 21, 2026 6:34 pm
by 944er
What are the lights on the relay doing when you have the starter engaged? That will be more useful than us reading the relay manual back to you.
Re: How to interpret Focus 9 DME diagnosic lights
Posted: Thu Jan 22, 2026 10:15 am
by chrischrischris
Thank you, that is very helpful. I guess if the alarm is keeping the car from starting then all lights would be OFF except for the first light: ignition switch.
I don't think my alarm is keeping the car from starting. I installed the jumper wiring to the alarm harness and the diagnostic lights are the same as before: the ignition sw and fuel injection power both illuminate with the key and both fuel pump lights illuminate while cranking.
I know my fuel pump is good because I can hear it running when I jump the connections at the DME relay. Fuel pressure is not possible for me to measure currently as I am on a road trip, but I'm going to assume it is OK since the car will run perfectly once it gets started. However, I do have a spare fuel pressure regulator that I could try.
Cranking the engine multiple times doesn't get it to run. But, if I depress the accelerator pedal then it will start. This is a good clue for me. Does opening the throttle call for more fuel which allows the car to complete a cold start? Without my foot on the gas, am I lacking enough fuel for a cold start? Does this point to a bad DME temp sensor which should be providing the needed enrichment? For $20 I will definitely buy the sensor but trying to be logical in my approach.
Once started, the car will restart immediately.
Re: How to interpret Focus 9 DME diagnosic lights
Posted: Thu Jan 22, 2026 10:44 am
by Tom
chrischrischris wrote: Thu Jan 22, 2026 10:15 am
Thank you, that is very helpful. I guess if the alarm is keeping the car from starting then all lights would be OFF except for the first light: ignition switch.
I don't think my alarm is keeping the car from starting. I installed the jumper wiring to the alarm harness and the diagnostic lights are the same as before: the ignition sw and fuel injection power both illuminate with the key and both fuel pump lights illuminate while cranking.
I know my fuel pump is good because I can hear it running when I jump the connections at the DME relay. Fuel pressure is not possible for me to measure currently as I am on a road trip, but I'm going to assume it is OK since the car will run perfectly once it gets started. However, I do have a spare fuel pressure regulator that I could try.
Cranking the engine multiple times doesn't get it to run. But, if I depress the accelerator pedal then it will start. This is a good clue for me. Does opening the throttle call for more fuel which allows the car to complete a cold start? Without my foot on the gas, am I lacking enough fuel for a cold start? Does this point to a bad DME temp sensor which should be providing the needed enrichment? For $20 I will definitely buy the sensor but trying to be logical in my approach.
Once started, the car will restart immediately.
If you can get it to run by pumping the gas pedal, then the DME relay issues are likely moot and it's more likely a air-fuel ratio issue. The DME temps sensor (blue sensor) may be bad and telling the DME it is super cold and adding too much fuel. When you open the throttle you are letting in extra air that allows the mixture to ignite. Don't 'throw parts' at it though, as that sensor is just one of several possibilities. Use the guide linked below to test your temp sensor and let us know what you find. If you don't have a multimeter, I'd get one of those before spending money on a new sensor at this point. You can get them for peanuts these days, and they are a must-have tool for anyone hoping to work on their own 944.
https://www.carpokes.com/viewtopic.php?t=695
Re: How to interpret Focus 9 DME diagnosic lights
Posted: Fri Jan 23, 2026 3:08 am
by chrischrischris
Thanks Tom. I have a multimeter at my home workshop, but not with me currently. I can certainly purchase one, though. I agree it would be nice to test the sensor but will likely just replace. Seems like you are suggesting that these typically fail in a way that results in an overly rich mixture?
Re: How to interpret Focus 9 DME diagnosic lights
Posted: Fri Jan 23, 2026 7:44 am
by Tom
chrischrischris wrote: Fri Jan 23, 2026 3:08 am
Thanks Tom. I have a multimeter at my home workshop, but not with me currently. I can certainly purchase one, though. I agree it would be nice to test the sensor but will likely just replace. Seems like you are suggesting that these typically fail in a way that results in an overly rich mixture?
No, not suggesting that. They can fail open (rich) or shorted (lean) and the connector is prone to having frayed wires inside that will show the DME a shorted (lean) signal. Try pulling the connector off and seeing if the car starts easier. Could also be the air flow meter, fuel pressure regulator, injectors, HG, vacuum leak, DME, harness, etc., etc.