DTC 18 sets when the voltage on any injector circuit does not match the injector status. When DTC 18 sets, the PCM disables the driver for the injector with the incorrect voltage.

Each injector should have +/- 12 volts on the pink wire at the injector connector with the key on/engine off. The factory harness has a separate power wire to two groups of 4 injectors (#1/4/6/7 and #2/3/5/8), and each circuit is typically protected by a 7.5 amp fuse.

http://shbox.com/1/1995_pcm3.jpg

Each injector should have a resistance across the pins (connector off) of no less than 11.6 ohms to about ~16 ohms. Check resistance with engine cool.

The PCM supplies a ground to fire the injector. Best way to verify ground is to use a 'noid light, with the engine running.

 

I will check all of that out tomorrow. I’m having trouble downloading the data log to a video format to send to you, any suggestions?

 

You don't need to download the data to a video format. You need to use the software to record the data in a log file, export the data as a .csv file. That way I can load it into Excel and take a detailed look at the data. You don’t need to “send it”. You open a new post, click on “Go Advanced”, and use the “manage attachments” button to attach the .csv file to the post. Just like you would attach a photo to a post.

 

Thank you. Of you couldn’t tell I’m not a computer guy. When I have time I will do that

 

Al of the injectors are below 11 ohms #1 9.9 3)9.87 5)9.96 7)9.89 2)9.83 4)9.99 6)9.83 8)10.04. What does this mean?

 

Did you measure across the two pins on the injector, with the harness connector removed? Are these stock injectors or aftermarket? If aftermarket, what brand? I would also recommend checking the multi-meter by measuring a known resistance in the 10 to 20 ohm range, to insure the accuracy of the meter.

 

Yes the connectors were removed and I used a new fluke meter. All of the pink wires have 12.5v. The injectors are stock, and the wiring harness is an aftermarket kit from Texas cars for a jaguar. Not sure were to go from here? New computer?

 

The computer wants to see at least 11.6 ohms on each injector. That limits the driver current to about one amp. Too low resistance means the PCM injector driver is flowing more current than it is designed for, and the voltage on the circuit goes out of range. It appears to be an injector problem, not a PCM problem. The reason there is no pulse (ground) from the PCM is because the voltage on the injector circuit is out of range, so the PCM shuts the injector driver down.

I have never heard of all 8 of the injectors being out of spec. Something isn’t right, but it’s beyond me. Let me get GaryDoug's (Bert Bandit Reynolds) input.

 

Thank you for your help. I work on semi trucks for a living, and I do a lot of wiring. This is very baffling 😕😕😕

 

Ok I feel really stupid. I realized I was testing the wires and not the injectors. I will check those tonight after work 😢😢😢

 

OK.... because GaryDoug (electrical engineer) had been following this thread, and nothing made any sense to him either.

 

Well This go’s to show you that even some one that has 30 years of wrenching still makes mistakes 🤓🤓🤓

 

ok all of the injectors are 12.1 to 12.2 ohms. What else could it be?

 

I changed out the injectors and no change???

 

Since they were within spec, why did you change them out?