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This car has sat for around 3 years. It was given to me from my father in law. His health has been declining so his memory is not the greatest. The battery would not hold a charge so I got a new battery. He said the ECM was having troubles so I pulled it out. It has a lot of battery acid on it, but the wiring harnesses look okay. Do you think I need to replace the ECM to get it to start? It has power to the dash when I turn the key on. But it won’t do anything when I turn it to start. The check engine light is on, when the key is in the on position.
You took out the pcm? From the passenger front wheel well? Was it cranking? What does it do when you try and start it with the new battery?
yeah I took it out from the passenger wheel well. It was under the battery. Is that a PCM? Sorry for the wrong name, but yes that sounds correct. There was also a black box (looks like a fuse box of sorts) connected to the bracket of the PCM. I can’t get the lid off of it to look inside?
When I try to start it nothing happens, it doesn’t make any noises, just the lights go dim on the dash.
Hey Scott !!...sorry to hear about your father in law...what kind of trouble did he say the PCM was having ??...if it indeed had battery acid damage there is really no way to determine how bad it is...replacing and reprogramming it would be a smart option. The TAC module is the black box attached to it...a quick way to determine if the PCM is “alive” is to remove the connector off the MAF sensor and with a voltmeter see if you see 5 volts at the yellow wire with the key ON. As far as the “no start” since the car had been sitting for 3 years you can give the starter a couple “love taps” and see what happens...with the check engine light on can you use the DIC and see what DTC’s pop up ??...might help in some diagnosis !!...
does the security light (pictured) go out after a few seconds when the key is turned on ??...also since the car had been sitting for that length of time if the fuel system hadn’t been treated with some type of “Gas Stabilizer” you may have issues with fuel injectors once you do get it started !!
Hey Scott !!...sorry to hear about your father in law...what kind of trouble did he say the PCM was having ??...if it indeed had battery acid damage there is really no way to determine how bad it is...replacing and reprogramming it would be a smart option. The TAC module is the black box attached to it...a quick way to determine if the PCM is “alive” is to remove the connector off the MAF sensor and with a voltmeter see if you see 5 volts at the yellow wire with the key ON. As far as the “no start” since the car had been sitting for 3 years you can give the starter a couple “love taps” and see what happens...with the check engine light on can you use the DIC and see what DTC’s pop up ??...might help in some diagnosis !!...
does the security light (pictured) go out after a few seconds when the key is turned on ??...also since the car had been sitting for that length of time if the fuel system hadn’t been treated with some type of “Gas Stabilizer” you may have issues with fuel injectors once you do get it started !!
The security light does go off when the key is on. I will get some stabilizer for the gas, so when it starts that’s good to go. What is the MAF sensor? I am planning to get a new PCM. Do you recommend getting a new one from the dealer or online from somewhere? Thanks for all the help. The TAC module is that something I should replace also?
Maybe something is seized up. Check everything with a pulley. Could be the starter is jacked. This could turn into a for sure challenge. My first steps would be seeing if the engine turns and all pulleys are free. My next step would be to check all the power, grounds to the fuse box check fuses, relays. Check starter grounds and power. Drain the fuel. Replace it with some 91 and some dry gas. Maybe a gal or 2. Shake the car up. Replace that pcm. Then see what you got. Maybe you’ll get turn with no fire and replace the plugs and continue on with basic maintenance.
Is it a manual or automatic car? I agree, sounds like a starter solenoid issue. While someone is inside the car holding the ignition switch to CRANK, Like C5 DIAG suggested, whack the starter and see if it comes to life. The solenoid on the C5 are well known to do exactly what yours is doing.
Give it a good whack and see if it starts. While you are down there, make sure that the solenoid connections are clean and tight!
I have found a place to get the new PCM, I will order it tomorrow. Would the PCM keep it from starting? Should I look at pulling off the starter or wait until I get the new PCM? I have checked all the fuses and the lines into the fuse box, there was an in-line fuse that was blown to the fuse box, and I did replace it.
I have found a place to get the new PCM, I will order it tomorrow. Would the PCM keep it from starting? Should I look at pulling off the starter or wait until I get the new PCM? I have checked all the fuses and the lines into the fuse box, there was an in-line fuse that was blown to the fuse box, and I did replace it.
You have c5diag and bill, the two experts on this forum giving you advice. I’d follow it before you start buying parts.
I have found a place to get the new PCM, I will order it tomorrow. Would the PCM keep it from starting? Should I look at pulling off the starter or wait until I get the new PCM? I have checked all the fuses and the lines into the fuse box, there was an in-line fuse that was blown to the fuse box, and I did replace it.
It would sure keep it from starting ( it will crank though) depending how much damage was done...with the PCM out you should clean the surrounding area with baking soda and water to neutralize the acid and then use a good undercoating paint (I like POR 15) to the damaged areas. I’d smack on the starter and solenoid and see if it will start. If you have a voltmeter check that yellow wire at the MAF sensor...the 5 volt reference is the lifeblood of the PCM...it is used by many sensors in the car !!...oh, BTW what inline fuse was blown ??
The inline fuse was a 25Amp that runs power to the fuse box, right next to the battery. I will put the old PCM back on and smack the starter to see if anything will happen, I will let you know. What is the MAF sensor? Is the solenoid and the starter the same thing? Sorry for some unknown knowledge, I am construction savy but not too much auto savy!!
The solenoid is attached to the starter, it is an electro magnetic switch that sends battery voltage to the starter motor to engage the starter to the flywheel and crank the engine over.
I put the PCM back in and smacked on the starter, no luck same thing. It doesn't do anything when I turn the key all the way. I forgot my volt meter when I went over to put the PCM back in so I will take it over and check the yellow wire on the MAF sensor. I haven't ordered a new PCM yet, I still think I need to, just waiting for a week or so. Is there any way to check the starter if its good or not? I just didn't know if I should replace it first?
Connect your volt meter with a clip type test lead to the switch terminal on the starter solenoid, it is the small gauge wire usually violet color, and the other lead to negative terminal on battery. Have someone try to start your car while you verify if 12 volts is present when key is turned to start, if 12 volts is there it is your starter solenoid, if not there you then have to check if the TDR "theft deterrent relay" located in passenger footwell area above the BCM is being energized. If TDR is not being energized then you could have bad ignition switch contacts, bad clutch depressed switch if standard or bad Park/Neutral switch if automatic, and lastly the security light should come on and then turn off before turning the key to start.
Take it off. See if the bendix is free. You could replace the bendix or the starter it’s fairly cheap. If the motor isnt turning there are frozen parts. I would hold on on buying a pcm until the motor at least is free. Is it a manual or automatic? I know on autos if there’s anything wrong with the gear selection fuses, shift column, or transmission the car would fail to turn over as well. I would follow all the suggested diagnostic.If that fails pull the starter.if it’s a manual your possibly looking at something with the clutch starter engagement. Are you pushing in the clutch if it’s a manual? Or stepping on the brake if it’s a automatic? Sorry for the stupid question this does help narrow it down. It could be a simple 5 min fix.
Originally Posted by Scott Preston
I put the PCM back in and smacked on the starter, no luck same thing. It doesn't do anything when I turn the key all the way. I forgot my volt meter when I went over to put the PCM back in so I will take it over and check the yellow wire on the MAF sensor. I haven't ordered a new PCM yet, I still think I need to, just waiting for a week or so. Is there any way to check the starter if its good or not? I just didn't know if I should replace it first?
Last edited by Speedy007; May 2, 2019 at 01:00 PM.
I put the PCM back in and smacked on the starter, no luck same thing. It doesn't do anything when I turn the key all the way. I forgot my volt meter when I went over to put the PCM back in so I will take it over and check the yellow wire on the MAF sensor. I haven't ordered a new PCM yet, I still think I need to, just waiting for a week or so. Is there any way to check the starter if its good or not? I just didn't know if I should replace it first?
If you just want to see if the starter itself will operate just jump B+ (BIG red wire) at the solenoid to the starter stud (picture below)...just be careful under there...neutral/park, e-brake set, wheels chocked !!...jumping directly to the starter will draw a LOT of current and arcing so a very heavy wire will be required !!...with a 12 volt test light you should have 12 volts on the PURPLE wire when cranking...if it lights the solenoid will be the connection between the B+ wire and the starter !!... if you don't you have to work your way back up the starting circuit !!...to check starter ground connect 12 volt test light to battery NEGATIVE and while cranking the test light should NOT light when touching test light to the starter housing !!
1998 C5 won’t start
