1990 Pont GP - 3.1L No Start; Code 42

[bakerauto]

Car came in as no start. Replaced Crank Sensor, Wiring, Ignition Module. Bringing up Code 42. No continuous spark after first time trying to start.

Any suggestions? Thank you much.

[brianp87]

Why were sensor, wiring and module replaced?

[bakerauto]

Thought it was a good place to start. Got no RPMs when trying to start it.

[brianp87]

Check the injectors and there pulse

[bakerauto]

Will a shorted injector mess up RPM Signal?

[ricmorin]

Time for some testing. First thing is to scope the crank sensor. Make sure that signal is getting to the module. Powers and grounds to the module will need to be checked. By your description, there IS spark at first then it goes away? The ECM takes over spark control at 400 rpm, so the possibility of a bad ECM is there as well. Use the process of elimination. Check the Hi and Low reference lines from the module to the ECM.

[brianp87]

No you need to check voltage at the module to start. Then I would check inj pulse. Also check the wires to the crank sensor to see if they are possible backwards

[ricmorin]

Will a shorted injector mess up RPM Signal?

Possibly. Most drivers use discreet power supplies, but some of these older ecm's didn't work that way. Easy way to check is to remove the short.

[brianp87]

Didnt get done typing before you ric lol. Key point is to start at one point and test each component with the most likely being sensor

[bakerauto]

Ok thanks for all the input. Going to pull the intake. Let you know what I find then. (Have checked all of the above)

[steven kiser]

am i missing something here? why is the intake coming off? is there a loss of spark after initial crank along with injector pulse stoppage? look into ric's tip on 400 rpm. i'm seeing a note about a mem cal chip issue...........has anyone been monkeying around trying to juice this up with "computer chip" replacement? these systems are fairly simple but in their simplicity some are difficult if not impossible to properly diagnose. if you're testing continuity or ohms on this car please use the connector chart not the color guide. personally i always run into faded color issues on older cars especially when the harnesses and plugs are initially covered with a grungy mass of crapolla. this tends to lead to head banging. is the crank pulley seperating? have seen many of these, but as a rule not causing this particular issue.

[Tim Martin]

Hmmm. So, we got a code 42. Generally in the past when I diagnosed that code using the diagnostic flow chart I found the problem. By replacing the ignition module, that possibility probably has been eliminated but there could also be a wiring issue between the ecm and ignition module but the ecm is also a prime suspect in this situation. I am not understanding why the intake is coming off as that has nothing to do with a code 42, unless there is other issues not mentioned. I'd be scoping the circuits between module and ecm. If they are good and there is a rpm signal, I'd be hunting an ecm.

[brianp87]

what did you find out? Any luck or questions?

[brianp87]

what did you find out? Any luck or questions?

[bakerauto]

Car still in the shop. Will keep you posted

[bakerauto]

Just to give you an update on "our nightmare car". Ended up receiving "bad" ignition module from parts supplier!

[steven kiser]

gotta love it. i learned the hard way assuming that replacement parts are good. when i test something and replace a part and if the issue still remains i start all over again testing. i chased a battery draw for day's before i tested the battery i gad installed. it was junk.

[Tim Martin]

Just to give you an update on "our nightmare car". Ended up receiving "bad" ignition module from parts supplier!

I usually test even a new ignition module with the tester I have here in the shop. It's surprising how many new in the box modules there are that are bad. What ya really gotta love is when ya open the box of a supposedly new one only to discover someone has had this one out of the box, installed it already and now I got it. GRRRRRRRR!