SoCalManche Posted April 30, 2020 Share Posted April 30, 2020 I pulled out my ECM hoping to find visible, fried components inside, but from the looks of it, that does not seem to be the case. I'm pretty novice when it comes to testing electrical issues, so can someone tell me the appropriate way of testing the ECM to verify it is properly working? Thanks! Link to comment Share on other sites More sharing options...
eaglescout526 Posted April 30, 2020 Share Posted April 30, 2020 There’s a very special tool and Renix scanner that would test the ECU. I have the ECU tester but not the MS-1700 scanner. So if someone has both and can loan them then you can test it. You could also test it for power across the pins. But that’s all I got for testing that sort of thing. I’m sure an oscilloscope would help too. Link to comment Share on other sites More sharing options...
Minuit Posted April 30, 2020 Share Posted April 30, 2020 To test that on the bench you would need to essentially recreate the conditions under which it would be installed in the vehicle and you would need a fair amount of test equipment and more importantly, the knowledge to perform the tests. Any broken solder joints on the back side of the board? What makes you think the ECU is bad? That is typically the very last thing you suspect in a vehicle that is not running properly, after everything else involved with the issue has been tested good. Link to comment Share on other sites More sharing options...
SoCalManche Posted April 30, 2020 Author Share Posted April 30, 2020 Just now, Minuit said: To test that on the bench you would need to essentially recreate the conditions under which it would be installed in the vehicle. A lot of work, to be sure. Any broken solder joints on the back side of the board? What makes you think the ECU is bad? I tried to pull the board out but it didn't seem to want to budge...I didn't pry any harder because I didn't want to end up breaking the damn thing. As for why I was hoping something was fried....long story short I posted on here a year ago, trying to get my 'Manche up and running and I could not find the issue. It died on me while I was driving it because I ran out of fuel, and when I threw more in it, it would not start. After that: - Engine would fire with fuel added directly to throttle body - Fuel pump wouldn't prime when ignition was switched to ON - Fuel pump would engage with a fused jumper wire in place of relay - All grounds had been refreshed per Cruiser's Tips - Added a few grounds where Cruiser recommends within the engine bay I've seen in other posts that the ECU can be the cause of this issue that other members have had like this. Link to comment Share on other sites More sharing options...
eaglescout526 Posted April 30, 2020 Share Posted April 30, 2020 Modern ECUs have a higher failure rate than the old ones and Renix really stood behind the whole test the ECU as a last diagnostic resort if it is suspected to be bad. Link to comment Share on other sites More sharing options...
Minuit Posted April 30, 2020 Share Posted April 30, 2020 5 minutes ago, SoCalManche said: I tried to pull the board out but it didn't seem to want to budge...I didn't pry any harder because I didn't want to end up breaking the damn thing. As for why I was hoping something was fried....long story short I posted on here a year ago, trying to get my 'Manche up and running and I could not find the issue. It died on me while I was driving it because I ran out of fuel, and when I threw more in it, it would not start. After that: - Engine would fire with fuel added directly to throttle body - Fuel pump wouldn't prime when ignition was switched to ON - Fuel pump would engage with a fused jumper wire in place of relay - All grounds had been refreshed per Cruiser's Tips - Added a few grounds where Cruiser recommends within the engine bay I've seen in other posts that the ECU can be the cause of this issue that other members have had like this. Get the electrical manual for your year and trace the fuel pump relay trigger circuit back to the ECU. You may have a bad connection or broken wire somewhere. Link to comment Share on other sites More sharing options...
SoCalManche Posted April 30, 2020 Author Share Posted April 30, 2020 6 minutes ago, eaglescout526 said: Modern ECUs have a higher failure rate than the old ones and Renix really stood behind the whole test the ECU as a last diagnostic resort if it is suspected to be bad. Good to know! Thanks for the info! 2 minutes ago, Minuit said: Get the electrical manual for your year and trace the fuel pump relay trigger circuit back to the ECU. You may have a bad connection or broken wire somewhere. Will do. Headed down the rabbit hole now. Thanks. Link to comment Share on other sites More sharing options...
Pete M Posted April 30, 2020 Share Posted April 30, 2020 wait, did you try swapping in another relay? Link to comment Share on other sites More sharing options...
SoCalManche Posted April 30, 2020 Author Share Posted April 30, 2020 Yes, initially threw a new relay in and same issue persists. Actually, when I would swap out the new one and put the old relay back in, I remember it would start ticking sometimes? Just the old one though; the new one never ticked. The only way the fuel pump would turn on is by a fused jumper wire. That is still true today, as I've been messing with it for the last couple days now. Link to comment Share on other sites More sharing options...
Minuit Posted April 30, 2020 Share Posted April 30, 2020 The board is probably either screwed into the housing or held in by some type of plastic clips if I had to guess. But verify the circuit in the truck before looking harder at the ECU. Not saying it's NOT the problem, it's just the least likely cause of it by far. That looks to be a plated through hole board, which makes it somewhat less prone to bad solder joints. Just be glad it isn't made by the same people who made the factory radios for these trucks. Link to comment Share on other sites More sharing options...
eaglescout526 Posted April 30, 2020 Share Posted April 30, 2020 I have both factory books on the TBI and 2.5L. So if you need help diagnosing the books tend to help shed some light. Link to comment Share on other sites More sharing options...
AZJeff Posted April 30, 2020 Share Posted April 30, 2020 13 hours ago, Minuit said: The board is probably either screwed into the housing or held in by some type of plastic clips if I had to guess. But verify the circuit in the truck before looking harder at the ECU. Not saying it's NOT the problem, it's just the least likely cause of it by far. That looks to be a plated through hole board, which makes it somewhat less prone to bad solder joints. Just be glad it isn't made by the same people who made the factory radios for these trucks. It would not surprise me if the center of that PCB (printed circuit board) is attached with something like double stick foam tape (or an industrial equivalent.) A PCB that is only supported/attached at the edges/corners can flex up and down like an old oil can in the middle, leading to solder fatigue cracks. When I worked for Motorola, they made PCM's for Ford, and they were worried about PCB flexure as I described. To deal with this, Ford insisted that the early PCM's be "potted," which essentially encapsulated the PCB in epoxy. Needless to say, a potted PCB is unrepairable, and Ford quickly changed to supporting the PCB more evenly. I agree that looking for a problem with the PCM is the LAST thing to consider. Those devices are surprising reliable. If you become absolutely convinced the PCM is misbehaving, there are places that can test/repair them, but I don't know if they can deal with a Renix PCM. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 2, 2020 Author Share Posted May 2, 2020 On 4/29/2020 at 8:39 PM, Minuit said: The board is probably either screwed into the housing or held in by some type of plastic clips if I had to guess. But verify the circuit in the truck before looking harder at the ECU. Not saying it's NOT the problem, it's just the least likely cause of it by far. That looks to be a plated through hole board, which makes it somewhat less prone to bad solder joints. Just be glad it isn't made by the same people who made the factory radios for these trucks. On 4/29/2020 at 10:03 PM, eaglescout526 said: I have both factory books on the TBI and 2.5L. So if you need help diagnosing the books tend to help shed some light. Looking to pick your guys' brains. Did some back-probing on some connectors to try to locate where the issue is occurring. I'm having an issue with my multimeter maybe? When I test the O2 sensor connector, it reads 0.5-0.6, so not too shabby. However, when I try to test the MAP sensor connector or the other one ( can't think of the name currently) that connects directly into the TBI, the reading goes from 1 to blank. No 0, just blank like it shuts off. What's up with that? (Electrical diagnostics is not my strong suit) Also, I checked the resistance at the fuel pump connector, and it is reading 0.5 ohms as well. When I was checked the D1 connections: - D1_5 reads battery voltage - D1_2 reads 12 volts - D1_6 reads 2-something volts when relay is in the circuit; D1_6 reads 12 volts when fused jumper wire is inserted between pins 87 and 30. That's all I can think of at the moment. Thanks for any and all input thrown my way. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 2, 2020 Share Posted May 2, 2020 1 minute ago, SoCalManche said: test the MAP sensor connector or the other one ( can't think of the name currently) that connects directly into the TBI MAP sensor should be on the firewall. TPS is on the base of the throttle body. Every sensor should get ~5.0V with key on engine not running. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 2, 2020 Author Share Posted May 2, 2020 1 minute ago, eaglescout526 said: MAP sensor should be on the firewall. TPS is on the base of the throttle body. Every sensor should get ~5.0V with key on engine not running. Yes, I know the MAP is on the firewall; TPS is what I forgot. So I'm testing for volts, not ohms? I was back-probing the middle (B) wire on the three-wire connectors and it was going blank, versus the O2 sensor reading properly. If I'm to test for volts instead, which wire? A? Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 2, 2020 Share Posted May 2, 2020 A should be input and C is output. I have trouble back probing mine too from time to time, so its not just you getting that issue. TPS is not based on resistance. Also C is used to make adjustments for the TPS, usually between 4.6V-4.8V is the proper output for the TPS but I like to have it in the middle at 4.7V. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 2, 2020 Author Share Posted May 2, 2020 10 minutes ago, eaglescout526 said: A should be input and C is output. I have trouble back probing mine too from time to time, so its not just you getting that issue. TPS is not based on resistance. Also C is used to make adjustments for the TPS, usually between 4.6V-4.8V is the proper output for the TPS but I like to have it in the middle at 4.7V. MAP sensor: A - 0 Volts / C - 9 Volts TPS sensor: A - 3.65 Volts / C - 9 Volts Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 2, 2020 Share Posted May 2, 2020 Is the ECU back in the truck? 9V for output is really really high. OK had to get the TBI book C is the 5V circuit on the MAP, A is ground and B is output. MY bad. TPS is still the same as before. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 2, 2020 Author Share Posted May 2, 2020 1 minute ago, eaglescout526 said: Is the ECU back in the truck? 9V for output is really really high. OK had to get the TBI book C is the 5V circuit on the MAP, A is ground and B is output. MY bad. TPS is still the same as before. Yup, ECU back in truck. So is it bad that I'm 4V over for MAP and TPS? Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 2, 2020 Share Posted May 2, 2020 Its not a good thing when the book says the input should be 5.0V (+or- 0.5V) Terminal 16 of the ECU should also show 5V for the MAP circuit. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 2, 2020 Author Share Posted May 2, 2020 1 minute ago, eaglescout526 said: Its not a good thing when the book says the input should be 5.0V (+or- 0.5V) Terminal 16 of the ECU should also show 5V for the MAP circuit. Let me ask a question that just popped into my brain. How should I be testing the voltage? I was testing the same way I tested for ohms. Negative lead to negative battery post, and positive lead to respective connector. Also, MAP (B) is reading 3.9 - 4.1V. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 2, 2020 Share Posted May 2, 2020 Also the TPS input should be 5.0V with the throttle wide open and engine off at B and C. Jeez its been a while since ive done the TPS. I had them backwards. A is the output on the TPS and that should be 4.6V-4.7V. My bad. Good thing I have this book. Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 2, 2020 Share Posted May 2, 2020 7 minutes ago, SoCalManche said: Let me ask a question that just popped into my brain. How should I be testing the voltage? I was testing the same way I tested for ohms. Negative lead to negative battery post, and positive lead to respective connector. Also, MAP (B) is reading 3.9 - 4.1V. Ok MAPs output should be around 4-5V. 4.1V is fine. I would leave the ground probe in the sensor and use the power probe on the ECU connector and see if there is a voltage drop between the sensor and ECU. You can also test the MAPs ground Ohms at terminals 2 and 17. Link to comment Share on other sites More sharing options...
SoCalManche Posted May 2, 2020 Author Share Posted May 2, 2020 1 minute ago, eaglescout526 said: Ok MAPs output should be around 4-5V. 4.1V is fine. I would leave the ground probe in the sensor and use the power probe on the ECU connector and see if there is a voltage drop between the sensor and ECU. So then MAP, I would ground probe (A) and power probe (B), yes? As for TPS, my voltage is 1V lower than it should be, yes? How would one remedy that? Link to comment Share on other sites More sharing options...
eaglescout526 Posted May 2, 2020 Share Posted May 2, 2020 1 minute ago, SoCalManche said: So then MAP, I would ground probe (A) and power probe (B), yes? As for TPS, my voltage is 1V lower than it should be, yes? How would one remedy that? Yes, that will show you your output voltage with key one engine off at the sensor. Terminal 33 on the ECU should show the same output voltage. Ground testing the MAP for the ECU is done with probe in A and probe in terminal 17 of the ECU. You can also check the Ohms of the ground at the sensor and the battery to see how bad the resistance is. 5V is on C and use A for the ground. Then check terminal 16 on the ECU for the same 5V. For the TPS is that output or the 5V input? Link to comment Share on other sites More sharing options...
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