Having to replace ECU due to the EGR failure causing an issue with it. I have bought ecu with locks etc. Is there a way to change over without changing locks etc. My car is an 2004 2.5 MX5. Thanks in advance
You can code your existing key to the replacement PCM and immobiliser unit. I could potentially walk you through it. How many keys came with the replacement parts and how many existing keys do you have?
There is only 1 key with the replacement . I have 2 original keys. My ECU should be with me tomorrow.
I assume you’re getting the matched immobiliser unit too.
Let me know when you have the parts and the time.
I will do thanks
Is it necessary or advised to fuse the EGR before fitting the new ecu.
I’ve suggested fusing it in the past just in case, I have no evidence to prove it helps though…
Think I will to be sure
This is the text from the letters page in Soft Top Hardtop a few year back regarding fusing the EGR valve if it’s of interest to you.
"I have an NBFL 2003 1.8 and I’ve got the P1496/7/8/9 error codes showing up (i.e. open/short in EGR valve coils) and so have disconnected the EGR valve to protect the ECU, though I fear it’s too late as I’ve deleted the errors via the OBD socket but they keep coming back. My next intended steps are to do the resistance tests on the valve terminals and continuity tests of the wires from the valve to the ECU and have a good look at the ECU. In case the ECU is still OK, I want to fit the inline fuse(s) to protect it. Do I just need a fuse on the red/white wire, or any others as well? Can you tell me what amperage the fuse should be? Are there are other components that have red/white wires joining the one from the EGR valve. Do I need to worry that the short may have damaged other components in addition to the ECU?
Sincere thanks in anticipation of your advice,
Adam"
Robbie’s Reply
“The error codes will return with the EGR valve disconnected as the ECU will see an open circuit, It’s certainly worth trying a known good valve before writing the ECU off. There are 2 red/white wires going to the EGR valve that feed a pair of windings each, the red/white wires are supplied with 12 volts from the main relay. There is one wire coming from the main relay that splits off to various engine control components within the wiring loom. It feeds the mass air flow senor, the camshaft position sensor, crankshaft position sensor then finally splits off in 2 to feed the 4 EGR valve coils. The whole circuit is protected by the 30 AMP FUEL INJ fuse which is in the fusebox in the engine compartment. I would put 2 inline fuses in both of the red/white wires as close to the EGR valve as possible. I’m not sure what amperage fuses to fit, you’ll have to use trial and error, start with a very low one, say 3 amps and if that blows then put a slightly higher rated one in and see how that goes. Fit the lowest amperage fuse that you can which doesn’t blow during normal use. There is no guarantee that the fuses will protect an ECU from a failed EGR valve but I don’t see any harm in fitting them just in case. No other components should have been damaged by the EGR failure as when the EGR valves short out, they feed 12 volts directly into the EGR control part of the ECU, there are no other components on that part of the circuit.”
Follow up from Adam
“Just wanted to say a big thank you for your guidance, I have fitted a reconditioned EGR valve and 2 amp inline fuses on the red/white wires and now have no error codes! So obviously the ECU was still intact”
Thanks Robbie for your help so far it has encouraged me to become a fully paided up member.
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