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Hello have a spot of trouble with my 98 HSE the check engine light is not coming on and she will not start. Any help gratefully received.

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That sounds like you've lost a supply rail somewhere. IIRC GEMS should put the Check Engine light on until it receives a valid de-immobilise signal from the BECM.

If you've got some diagnostics that'll do it, it might be worth firing an Immobiliser Sync command at it just in case.

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No check engine is, as Gordon says, due to no power to the engine ECU. Usual cause it it having got it's knickers in a knot and lost sync with the BeCM. If you've got a Nanocom its simple enough to sort out but first check that relays 15 (Ignition on relay) and 19 (ECU power relay) are operating when you turn the ignition on.

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Thankyou well try that, many thanks 👍

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Have tried swapping relays around still no joy?

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Is it possible to bypass the relays to “prove” them?

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Yes, if you look they have 3 pins that are parallel to one another and one that is at 90 degrees to the others. You need to jumper between the one pin that is at 90 degrees and the one opposite it. Pins marked 30 and 87 here https://www.autoelectricsupplies.co.uk/image_uploads/140201-drawing_large.gif

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Thanks will try tomorrow

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Have bypassed the relays and can hear the right clicking noises but still will not crank over and no check engine light comes on?

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If the ECU and BECM are not synced, then there is no check engine light and no start. You will need a Nanocom to connect to the ECU and select utilities and security learn. In that way the next code the ECU sees from the BECM, regardless of what it is, it accepts as valid. That will then re-sync the two.

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Thankyou will try that next

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Error Unable to start communication with ecu?

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What year is the car? If an early car with pre V36 BeCM, it can't connect if the BeCM is in an alarm or immobilised state. Anything unusual on the dash?

Go into GEMS with the Nanocom, go to Diagnostics - Inputs - Engine Others and scroll through the pages until you get to Security Mobilised. If it says Yes, it is in sync, if it says No it needs to be put into Security Learn (on the same menu but it also appears under Utilities), turn the ignition Off then back on again. Security Mobilised should then change to Yes.

Don't forget that the Nanocom will only connect to the BeCM with the ignition OFF and the GEMS ECU with it ON.

When you say it won't start, does the starter spin it over and it doesn't fire or does the starter do nothing too?

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Thanks, will go through that in the morning. I jus get normal lights on the dash except the check engine light. Then last turn of the key just a small click. Can get the stater to turn if I bypass the relay.

I hope it is operator error, Many thanks.
She is a 1998 HSE

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On GEMS, a click from a relay inside the BeCM is all you hear if sync has been lost, so that, coupled with no Check Engine light, would seem to suggest that is the problem.

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Thankyou will keep you posted

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Security is set at No and I am not able to change it?

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you need to select "security learn" i think its on the next page?

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Yes, next page, Security Learn, Ignition off then back on, security then should say Yes.

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Thankyou all weather has been a bit rough so waited for a break in the clouds took the battery off charge turned the key, check engine light and she started up. Very happy and went for a quick drive.
Thanks once again.