ar_323 Posted March 26 Share Posted March 26 Hi Y’all, im trying to diagnose a E042 code. I have replace the magnavox coil packs with delco kind along with the 14pin connector that has been soldered to the original wire harness. When going through the diagnose tree. I get stuck on step 4 where ohms on wire BC8 (white) should read over 6000 ohms which it doesn’t. It continues to read around 140 ohms of resistance just like in step 2. Then in step 5 I disconnect the ICM 14pin connector then measure resistance and my multimeter continue to say OL/ off limits. Does that mean I got a faulty ignition module? I checked for continuity of wire 423 and 424 from the ECM and ICM Connector and they were good. I also found that wire terminal 121 (white) has continuity with terminal BC8. any suggestions from you guys? Link to comment Share on other sites More sharing options...
2seater Posted March 26 Share Posted March 26 I wonder if any readings through the ICM are valid in this diagnostic tree? I do not know the answer. While the Delco ignition is a plug and play replacement for the Magnavox style, some resistance and/or voltage readings may be different. This is only a question. Does a 1991 diagnostic tree have different values? Purely a guess, but I would guess the ICM is bad, especially if used. Swapping to a know good setup would at least narrow the focus. Sorry for the non answer Link to comment Share on other sites More sharing options...
Ronnie Posted March 26 Share Posted March 26 11 hours ago, ar_323 said: When going through the diagnose tree. I get stuck on step 4 where ohms on wire BC8 (white) should read over 6000 ohms which it doesn’t. It continues to read around 140 ohms of resistance just like in step 2. When you do the test for the 140 ohms, from the way I read the instructions, it says to have the ECM disconnected. Although I don't see where it is specified in the instructions, I wonder if you shouldn't have the ECM connected when you test for the 6000 ohm reading. Do you have the ECM disconnected when you are testing for 6000 ohms? Link to comment Share on other sites More sharing options...
Anthony Posted March 26 Share Posted March 26 (edited) There is much more information on how the bypass and EST circuits work, and how code E042 is determined in section C4 of the manual under the heading Electronic Spark Timing. What is failed to mention in these two pages is that the ICM's job is to ground the EST circuit until the ECM tells it to stop (after RPM reaches 400). Your test revealed that the ICM is grounding the EST circuit properly, however when you commanded it to stop doing that (by energizing the bypass circuit with a test light), the ICM kept grounding the circuit. It should have released the ground and allowed the ECM to send the EST pulses on that circuit (423). Since you've already checked for continuity on 424 and replaced the connector, the only remaining option is a faulty ICM Edited March 26 by Anthony 1 Link to comment Share on other sites More sharing options...
DAVES89 Posted March 26 Share Posted March 26 Anthony please hang around I think we need you. I am a plug and play guy with a lot of known good replacement parts. I just swap in parts starting with what parts are common to fail and go from there. My service manuals are hardly used... 1 1 Link to comment Share on other sites More sharing options...
Anthony Posted March 27 Share Posted March 27 10 hours ago, DAVES89 said: I am a plug and play guy with a lot of known good replacement parts. I just swap in parts I'm with you on some things. When my ECM went bad, I thought about taking it apart to find out what went wrong. I took one look inside and decided against it Link to comment Share on other sites More sharing options...
ar_323 Posted March 30 Topic Author Share Posted March 30 So I bought a new ICM. Under is a link of the ICM I bought. I installed it and made sure it has good ground by cleaning its base. now the vehicle doesn’t start. The engine turns but it seems like if the wires were placed in the wrong place. Are all ICM’s the same? I wonder if the new ICM is making the spark plug wires fire differently. https://www.ebay.com/itm/256160658287?chn=ps&norover=1&mkevt=1&mkrid=711-117182-37290-0&mkcid=2&mkscid=101&itemid=256160658287&targetid=1645685074048&device=m&mktype=pla&googleloc=1013915&poi=&campaignid=20133407470&mkgroupid=147476396765&rlsatarget=pla-1645685074048&abcId=9312979&merchantid=114154961&gad_source=1&gbraid=0AAAAAD_QDh-Y0Mcws-uvgRGvDAI7-S5ph&gclid=Cj0KCQjwzZmwBhD8ARIsAH4v1gUpTIQ0_5_BH7UoMCzWx-rdWMUNWE1LZjCErze4tGBK7CXzetH5ZU4aAs2KEALw_wcB Link to comment Share on other sites More sharing options...
2seater Posted March 30 Share Posted March 30 If that is the part number, it should be the correct ICM. There is a similar one used on the 3300 Buick engines in the Century in the early 90's which looks the same or very similar, but it is a different part number. The 3300 is the little brother to the 3800, but it uses a batch fire fuel injection system with no cam sensor. I do not know if they will plug together, or not, but the pinout may be different? I don't know, just musing. If the ICM's are tested with the breakout box as shown in the ad ??? Was this a change from a Magnavox to the Delco style? I lost track. Situations like this reinforce the need to have a known good backup system to try as a substitute to rule out other possibilities. Link to comment Share on other sites More sharing options...
rogold Posted March 30 Share Posted March 30 My last ICM I bought had the cylinder numbers embossed in the plastic by the contacts that plug into the bottom of each coil 1-4, 5-2, 3-6. Link to comment Share on other sites More sharing options...
2seater Posted March 30 Share Posted March 30 All coilpacks, Magnavox or Delco, arrange the plug wire connections the same: 6 - 3 Top view -> 5 - 2 4 - 1 Harness connector end It does not matter which plug wire connects to which terminal as long as they are correctly paired. 1 Link to comment Share on other sites More sharing options...
ar_323 Posted March 30 Topic Author Share Posted March 30 I read Padgett how to guide for the delco conversion. He described the same issue as I have when swapped his ICM. It is a hit and miss with these ICM, the car might or might not like it. One of these days will go to the junkyard to get a few ICM. also saw that the junkyard had a 89 eldorado. Any parts that are shared in the reatta? Link to comment Share on other sites More sharing options...
ar_323 Posted April 2 Topic Author Share Posted April 2 I got different ICM and I still got the E042 code. I went through the diagnostic tree again and found out that my ECM was faulty. Swapped ECM and saw that I got prom ASSU1614. Can anyone provide a correct prom for my vehicle? Link to comment Share on other sites More sharing options...
rogold Posted April 2 Share Posted April 2 If your old ECM had the correct prom in it, you should be able to swap it to the new ECM. Link to comment Share on other sites More sharing options...
ar_323 Posted April 2 Topic Author Share Posted April 2 My old ECM has the wrong PROM. It seems to me that the previous owner swapped the ECM without swapping PROM’s. Link to comment Share on other sites More sharing options...
2seater Posted April 2 Share Posted April 2 Is that Prom ID direct from the part? ASSU is the latest 1989 Prom listed in the How To guides above? According to the notes, that Prom was issued after 1989 production ended. Do you get any sort of communication error codes in diagnostics? Link to comment Share on other sites More sharing options...
ar_323 Posted April 2 Topic Author Share Posted April 2 (edited) My original ECM had the PROM ASSU1614. I do not see the prom anywhere in the how to guide notes. I tried using the a different ECM with prom ASSU1614 and I got the E042 code. Either I got the wrong PROM or bad ECM. The diagnostic tree leads me to a faulty ECM. anyway to test the ECM? Edited April 2 by ar_323 1 Link to comment Share on other sites More sharing options...
Ronnie Posted April 2 Share Posted April 2 This is off the wall but... I'm wondering if the problem isn't with the crankshaft position sensor or associated wiring. It puts out two signals to the ICM. A 3x signal and a 18x signal. It can start and run on just one (don't remember which one) but maybe without both signals it can't go into ECM control of the spark and would throw a code E042 when it senses the RPM is over 600. 1 Link to comment Share on other sites More sharing options...
ar_323 Posted April 2 Topic Author Share Posted April 2 I check with sinister performance and he told me I had the right EPROM so I am at a loss here. I ran the car with the eprom from bonneville from the same year range and engine and the code did not come up. at this point I might assume that the replacement ECM is also faulty. Link to comment Share on other sites More sharing options...
Anthony Posted April 2 Share Posted April 2 It's very possible that both ECMs are faulty. Where did you get the replacement ECM? Link to comment Share on other sites More sharing options...
ar_323 Posted April 2 Topic Author Share Posted April 2 From the eBay store you brought yours from. Swan Auto. @Anthony when you brought the two ECM’s from rock auto how did you know you had faulty ECM’s? Link to comment Share on other sites More sharing options...
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