P1670 on a 2000 V70 not responding to the usual fixes

3p141592654 · Post by **3p141592654** » 01 Aug 2023, 15:13

As the title says I expected to conquer this one quickly with a new antenna ring but no such luck. Both keys tried and do not work. Cleaned the connector and back probed with connector attached confirming good 5.5 ohm connection to ring. With connector off read 75k ohms confirming wiring good to immobilizer box. Cycled the connector on the immobilizer box and the CEM. Checked immobilizer specific fuses per wiring diagram and they are good.

Car starts and runs for various short time periods like .5 to 5 seconds. Fuel pressure is good. No other codes present.

I'm out of ideas at this point. Any suggestions?

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Post by **scot850** » 01 Aug 2023, 16:20

If the engine turns over, then I believe the immobilzer is not the issue. I understood the immobilizer prevents the engine turning over, ie. kills the starter circuit. I am happy to be corrected on this.

Assuming your keys are the correct ones, and that nothing else has been changed in the system then I am also not sure what is going on.

For clarity, you have tested the fuel pressure (for your car should be >50psi). You have tried a jumper or a spare fuel pressure relay?

Have you tried swapping the electrical portion of the ignition key barrel?

Neil.

3p141592654 · Post by **3p141592654** » 01 Aug 2023, 20:50

Thanks for the ideas. Based on what I've read and my own experience the immobilizer does not prevent starter cranking. It seems to cut the fuel pump based on my observations which is why it runs for a few seconds then quits.

3p141592654 · Post by **3p141592654** » 06 Aug 2023, 16:47

Debugging continues. VIDA shows IMM-321 Faulty comms consistently. I am going to have to verify the wiring between the ECM and the immobilizer modules. VIDA shows the IMM is recognizing the key and giving a positive signal to start. At his point it looks like either wiring or the ECM itself is bad.

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xanthefin · Post by **xanthefin** » 07 Aug 2023, 00:19

(i did read first time wrong so i corrected my text)
Well as you get positive Response and Question rec. in live data so Immo responds ECM ok.
(Additional clarification: Immo is told all clear and it doesnt anymore stop engine running during start)

This fault code happens too if there happens a unusual reset like engine cut off other reasons.

You say it runs even up to 5 seconds. Thats would be for me a clear signal its not about Immo as it always only gives time for two seconds (including crank) when Request was not received or not positive.

How this works is that ECM sends request to IMMO first always after you turn ignition On. Immo then responds back was it positive or not correct data (communication is fully encrypted, it includes random calculation plus engine code).

My best guess this fault code gets registered if there comes new request before Immo box gets shut down (like if there was already one successful one or it become too late but this would be registered in live data and NOT show all Positive in Response).

I have once read this fault code can come too if you have bad fuel pump.

Does your fuel pressure drop when crankin or starting happens too much?
Does your battery go too low during crank?
What data shows on ECM side? You lose connection during crank to it?

Maybe ECM resets unusual way during crank and asks again Immo some nonsense.

3p141592654 · Post by **3p141592654** » 07 Aug 2023, 15:53

Wow, thank you for the response. The time it runs is variable and sometimes is long enough that I am about to celebrate and then it starts to stumble and then stall. Sometimes it won't even fire during cranking. Its highly variable.

The fuel pressure seems good although I observe some variation between 40 and 60 psi. I don't know if that is normal or not. I have watched the fuel pressure hold steady while the engine runs fine and then start to stumble and then stall.

It has a few months old battery fully charged. I leave the charger on all the time. During cranking I never see +15 bus go below 10V at the ignition switch during cranking. Is there anywhere better I should monitor voltage?

How do I monitor the ECM connection during cranking? I generally only look at VIDA with the engine stalled. The ECM data appears normal although it does register ECM-720A as a yellow.

I measured voltages on all the poles at the ignition switch and they seemed steady and normal 12 V. Based on your analysis, I think it would be good for me to monitor the supply voltages at the ECM and look for any glitches or brownouts.

3p141592654 · Post by **3p141592654** » 22 Aug 2023, 11:08

Very frustrated with this problem. First, fuel pressure is 60psi and steady. The only codes that ever show up are ECM720A and IMM321. They are intermittent though. Typically only about 30% of the time and I now feel they are just spurious, a results of starting a stalled engine many times with various delays and sequences. The root cause is something else. I have pulled the IMM and resoldered the connectors. I have pulled the ECM and it looks physically fine. All grounds are present and accounted for.

Last week I disconnected the MAF and low and behold the car started and ran just fine. So I figured it was a bad MAF that was giving erroneous data but not enough to set the CEL. Swapped in a new MAF and it ran great and drove it around the block. Ran perfect. Hurray! Put the underdash cover back on and was ready to celebrate. Tried to start the car and back to square 1. Started and stalled. Grrr.

The only thing I notice that seems odd is that the live data from VIDA updates so slow as to be useless. We are talking update rate of like one data point every 5 seconds. It is so slow that I cannot get any data during the few seconds that the engine runs after starting. Is that normal? I cannot remember. Seems like it is not. VIDA shows green on all modules. I am so confused.

3p141592654 · Post by **3p141592654** » 12 Sep 2023, 11:25

Tried replacing the B+ wire and repinning the connectors for the immobilizer. If anything the car was worse afterwards, cutting out even when driving which it didn't do before.I considered reflashing the ECU, but it really wasn't worth anymore investment to us. Sadly it went to crusher. After 23 years it was time to go.

Post by **scot850** » 12 Sep 2023, 11:33

That is a shame, but it was not for the lack of trying. Sorry for the loss!

Neil.

3p141592654 · Post by **3p141592654** » 15 Sep 2023, 10:39

Thanks. Yeah, it was sad to see it go, and frustrating to be unable to solve it.