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Jerry
Jerry, Master Mechanic
Category: Dodge
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Experience:  ASE Master tech, 30 years exp. troubleshooter, driveability tech
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1994 B250 Van 5.9L trouble code 27 - Injector output circuit

Customer Question

1994 B250 Van 5.9L trouble code 27 - Injector output circuit not responding. Intermittent check engine light although it is on more than off. Engine running rough, bogs before it will accelerate, smells like it is running rich. Problem started after replacing the PCM because of a crank no start issue (made sure replacement PCM had the exact same part number). All 8 injectors ticking - did the screwdriver to the ear thing. They all tick regardless of whether the engine light is on or off. I'm assuming that means all are receiving the signal from PCM. Checked continuity of all injectors with no real variance in the readings. Any suggestions on what might be going on? I can't even tell which circuit is causing the problem. Is it possible that this could be a fuel pressure thing? Thanks.
Submitted: 1 month ago.
Category: Dodge
Expert:  david craig replied 1 month ago.

Hi Im David, just because they are all getting command from the PCM doesnt mean they are all responding properly even with the resistance reading close to each other. the proper resistances should be around 14.4-14.7 ohms.

Customer: replied 1 month ago.
Hence the code .... resistance readings show 15.2 - 15.4. I attribute the variance from spec to my ohmmeter as it just doesn't seem logical to have all 8 injectors become problematic at the same time and to the same extent.What would be useful is any insight as to what would cause the improper response and how to narrow it down to which circuit is causing the problem. I need detailed step by step instructions for any testing that might be helpful.I asked about fuel pressure being a possibility because last night after adding a few gallons of gas to the nearly empty tank I started the van again and the check engine light was off and it has stayed off so far (although I have only driven about 15 miles since getting gas). The fuel pump was replaced about 4 years ago and I have been told that it is common for them to go out again rather quickly. I believe the fuel pressure regulator is within the fuel pump?Thanks for your help
Expert:  david craig replied 1 month ago.

here are a couple of prints to familarize yourself with the syatem

Expert:  david craig replied 1 month ago.

the fpr is indeed located in the tank within the intank fuel filter.

Expert:  david craig replied 1 month ago.

whats the voltage at the battery while the engine is running if i may ask?

Customer: replied 1 month ago.
I haven't checked battery voltage while running but will do that.I repeat "What would be useful is any insight as to what would cause the improper response and how to narrow it down to which circuit is causing the problem. I need detailed step by step instructions for any testing that might be helpful."
Expert:  david craig replied 1 month ago.

i need to know the voltage with the engine running at 2500 rpms. then we will worry about a step by step. i dont like to get ahead of myself. if thats not acceptable to you, i will opt out and allow another tech to chime in. thank you.

Customer: replied 1 month ago.
battery voltage bounced between 14.4 and 14.5
Expert:  david craig replied 1 month ago.

ok, thats good. we will pick this up tomorrow. its almost 1am here. got to get some sleep.

Customer: replied 1 month ago.
I neglected to mention that last night when checking battery voltage the check engine light came on within 30 seconds of starting the van.
Customer: replied 1 month ago.
This thread covers the same error code:http://www.justanswer.com/dodge/31m0f-1994-dodge-ram-wagon-2500-5-2l-8cyl-mpi-intermittent-error.htmlThe following testing is included within it but I'm not clear on the instructions."Locate Pin 57 first... this is your autoshutdown (ASD) relay output circuit, which is shared between the injectors, coil, oxygen sensor heater and the PCM. Connect one of your ohm meter test leads to this terminal, being careful to avoid spreading the terminal.The other one will be connected to each of the eight injector control circuits, 13-18, 38 and 58. Each of these circuits will be complete circuit tests between the power source (ASD) and the end product-control. In between will be all wiring, connectors and injectors to influence what you see as an end result. Use the 200 ohm setting on your meter for this testing.Connecting the ASD test lead to battery negative while checking each control circuit individually will show any continuity to ground... which should never happen when tested in this manner. Set your meter to 2K ohm at least... maybe higher yet.The only thing this test won't show is whether the 60-way terminal is too loose or if the PCM circuit driver is bad. But it's a good start, as is performing the index procedure if you get the time."I can't determine whether the testing is done with all leads on the computer side of the connector or if on the 60pin connector or whether the connector is connected to the computer or whether the engine is running or key just on or? I don't want to do it wrong and risk possibly frying some component.
Expert:  david craig replied 1 month ago.

ok. let me look at the procedure.

Expert:  Juan Crespo replied 1 month ago.

Hi there. Different expert here.

Before OBD-II came along, Chrysler used two-digit codes that were not very explicit - in your case, code 27 indicates a problem with the injector control circuit; it doesn't specify which injector or what part of the circuit. Because of its complexity, this type of diagnosis was usually handled only by the top diagnostic technician at the dealer.

The key to this diagnosis lies not only in the technical knowledge (which I can certainly provide), but also in the tools you use; you'll need a DRB-II/DRB-III or equivalent bi-directional scan tool that can actuate each injector individually or, preferably, a scope with a low-amp probe attachment that can show the current being used by each injector - that will allow us to isolate the circuit causing the issue. Do you have access to any of those tools?

Customer: replied 1 month ago.
My neighbor loaned me his DRB II with all the bells and whistles but the connector is different (although it fits his '98 Dodge truck) so couldn't use it.. Do they make an adapter? Otherwise I'll have to take it to a shop to diagnose which is not really within my budget.
Expert:  Juan Crespo replied 1 month ago.

I'm sorry, but it looks like I won't be able to help you. I'll opt out so others may try. Please don't rate or reply until another expert responds or the site will cycle this back to me.

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