Need help with p0203 code

[Rawbin24]

SES light plus rough idle, checked code and got p0203. Sent out fuel injectors for cleaning, re-installed and car felt great. Next day SES light, rougher idle and p0203 code.

I will swap injectors around to check it’s not #3 but beyond that not sure what do next. Do I go straight into purchasing a an injector wiring harness loom off eBay or do I buy a DME and flash it myself? Any input is appreciated.

Wiring Harness.

https://www.ebay.com/itm/256574377763?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=nXAayOsfR9q&sssrc=4429486&ssuid=zsB2K1pmT8u&var=&widget_ver=artemis&media=COPY

[Rawbin24]

Bump

[Rawbin24]

Bump, need help. Any input is appreciated.

[sapote]

You have a voltmeter?
The injector connector has 2pin: one is 12v when key turned on, and the 2nd pin is 12v and drops to 0v when DME injects fuel.

To test: disconnect the big black cable off the fender 12v jumper post, to prevent starter accidentally cranking with your hand in there. Car in neutral.

key turned on, check one pin for 12v supply and this pin should always be 12v when manually turn the crank CW. The other pin should be mostly 12v but it's pulled down near 0v while turning the crank manually.

Report back.

[Rawbin24]

Thanks for the advice. Is this what you are referring to disconnect? And when you say crank manually, are you referring to do so via the crank pulley or crank with the key?

[sapote]

Thanks for the advice. Is this what you are referring to disconnect? And when you say crank manually, are you referring to do so via the crank pulley or crank with the key?

Yes that jumper post cable. With the cable disconnected the starter is disabled.

[sapote]

To test: disconnect the big black cable off the fender 12v jumper post, to prevent starter accidentally cranking with your hand in there. Car in neutral.

key turned on, check one pin for 12v supply and this pin should always be 12v when manually turn the crank CW. The other pin should be mostly 12v but it's pulled down near 0v while turning the crank manually..

I found out today that manually turning the crank doesn't trigger the ignition coils for sparks, so I think the same is for injectors. You need to use the key to crank to trigger the injectors to be sure.

I think it's a safety design so the engine not accidentallly start running when tech manual crank during testing. The DME needs to see above a threshold rpm for it to fire the sparks and injectors.

[Rawbin24]

I found out today that manually turning the crank doesn't trigger the ignition coils for sparks, so I think the same is for injectors. You need to use the key to crank to trigger the injectors to be sure.

I think it's a safety design so the engine not accidentallly start running when tech manual crank during testing. The DME needs to see above a threshold rpm for it to fire the sparks and injectors.

Thanks for the follow up. And after testing and confirming with the voltmeter, do I replace the entire wiring harness as shown in the eBay link? It seems like a pain since it snakes under the block and intake manifold.

[sapote]

Thanks for the follow up. And after testing and confirming with the voltmeter, do I replace the entire wiring harness as shown in the eBay link? It seems like a pain since it snakes under the block and intake manifold.

The code points to #3 injector, so depending on what your test result is, maybe just need to repair one wire (add a new wire) from DME to injector connector, not needing to replace the whole harness.