prom id 89 iroc

on my scan tool it says prom id 541 is this correct my book gives typ data but I have not found a ref for this yet Thanks in advance

on my scan tool it says prom id 541 is this correct my book gives typ data but I have not found a ref for this yet Thanks in advance


5.7 engine vin 8 pcm no 1227165 fed emissions 700R4 transmission with a 2.77 rear end I show a 541 prom but it has a updated prom for a running change.
What is your model and engine and trans and engine code and pcm no. ?

5.7 l98 700r the ecm # the same so the prom is the rightone, Im having a hard start issue just wanted to make sure.the 89 was last one with a maf and the first one with out the cold start injector, thought maybe it wasnt pulsin the injecors enough on start up.Im getting rpm on the scan and the inj noid light blinks on both sides but it dont pick up the base pulse width till the engine starts.I got another post for iroc dont start some times . Thanks

5.7 l98 700r the ecm # the same so the prom is the rightone, Im having a hard start issue just wanted to make sure.the 89 was last one with a maf and the first one with out the cold start injector, thought maybe it wasnt pulsin the injecors enough on start up.Im getting rpm on the scan and the inj noid light blinks on both sides but it dont pick up the base pulse width till the engine starts.I got another post for iroc dont start some times . Thanks

You might put a scanner on it and check all sensor data.
Watch and make sure tempt sensor data are correct.
Maf sensors and pcm gave a lot of trouble on them.

I have a mt2500, all the sensors are in range tps, coolant,maf, iac, rpm, ect Ive replaced almost all of and the ecm, the cars perfect when its runin and will start most of the time it might start ,then you turn it off and it wont start ,itll start okay in the morning you go to the store go in come out it will start then you go home go in come out it will start but if you turn it off and try to start it right away it wont. You spray little carb cleaner inthe intake it starts rit up, the scan data is all ways consistent, the physical checks are okay(fuel pressure, volume, blinking noid light, spark ect)The only thing my book says that I havent checked is that the egr might stick open causing a lean condition but know body buys that. Its frustrateing

I have a mt2500, all the sensors are in range tps, coolant,maf, iac, rpm, ect Ive replaced almost all of and the ecm, the cars perfect when its runin and will start most of the time it might start ,then you turn it off and it wont start ,itll start okay in the morning you go to the store go in come out it will start then you go home go in come out it will start but if you turn it off and try to start it right away it wont. You spray little carb cleaner inthe intake it starts rit up, the scan data is all ways consistent, the physical checks are okay(fuel pressure, volume, blinking noid light, spark ect)The only thing my book says that I havent checked is that the egr might stick open causing a lean condition but know body buys that. Its frustrateing

Give the EGR valve a test/check when it does not start.
And you may want to check fuel prerssure when it no sart.
Most of the time a pcm is what throws off injector pulse.
Is TPS sensor and MAF sensor good?
I can not think of anything else.

Ok, so you are saying that if you run it and get it hot (operating temp) then turn it off and try to start it, it won't start?
If that is the case, get your ohm meter ready. Start the car and get it up to temp, shut it off and try starting it. Keep at it until it refuses to start. Then pull the injector clips and ohm out each injector. If you get anything below 12 ohms or over 18 ohms, the injector is bad. If they all ohm out good and it still won't start, try the noid light again.
What it sounds like you have is a heat related problem. Either the windings in the injectors is breaking down with heat or the ignition module is and not sending the ref pulse to the ECM.
The 89 PROM is programmed to NOT fire the injectors for the first 10 ref pulses. This was GM's way to ensure that there was sufficent oil pressure to start the engine. Personally..it is a royal pain. I reprogrammed my ARAP .bin file to get rid of that so the engine fires right up.

Ive ohm them out before all at 15, I will try again,The egr is just a pain I cant get my fat finger under the plenum to push on the diafram, Morely do you know , my book says it dont matter how bright the noid flashes as long as it does ind ecm control, but it does flash rather dim compared to when the car is running.For the record the maf and its connecter are new, the tps is new set at .54, the kaf usualy reads 5 or 6 thanks guys

Ive ohm them out before all at 15, I will try again,The egr is just a pain I cant get my fat finger under the plenum to push on the diafram, Morely do you know , my book says it dont matter how bright the noid flashes as long as it does ind ecm control, but it does flash rather dim compared to when the car is running.For the record the maf and its connecter are new, the tps is new set at .54, the kaf usualy reads 5 or 6 thanks guys

You might want to check the ign module.
It has to be working right to give PCM a RPM signal and start the PCM up and squirt injectors.
Good Luck

wow !i have that same exact problem and i have changed distributor and every sensor exept the ecm? the car was prked for 5 years would the ecm go bad?

I cant get my fat finger under the plenum to push on the diafram, Morely do you know , my book says it dont matter how bright the noid flashes as long as it does ind ecm control, but it does flash rather dim compared to when the car is running.For the record the maf and its connecter are new, the tps is new set at .54, the kaf usualy reads 5 or 6 thanks guys
I use a Mity Vac, vacuum pump to actuate my EGR and use a small inspection mirror to watch it move open and closed.
The noid light won't be very bright when cranking the engine, the starter and ignition system hog a lot of juice.
I still think it is a heat related problem, if it will crank right up when cooled off a bit. If you've replaced the ignition module...make sure it is an AC Delco. If it is a Wells, GP or other "Jap crap" module, that would my first guess as to the problem. The other mfg's don't use the demanding tolerances that AC does.

scan tool reads the rpm so the ecm getting the pulses,and replaced ign mod and the pickup in the dist, I have trown parts at this car off and on for 9 months weve done all the typ things I bought the snapon scanner on ebay so I could quit takin it to the shop for them to say it cchecks out, hell Ive stump the local guys and the dealer they all scream ecm but im on my third one the ecm is fine .....I have not physicaly held the fuel rail up and watch the inj spray but the light blinks on all off them and it runs good when it runs and some times it starts without missin a beat, Im gfonna trow an egr on and pray to the gm gods that their happy finaly

Since you say you have replaced the ECM, check the memcal. Get a magnifying glass and look at all of the solider joints and look at the under side where it plugs into the ECM. You may have a recessed pin on it that makes intermittant contact when it gets heated up or a cracked solider joint that seperates when hot.

i tried putting the car in limp mode and it will start eveytime I know it uses the oil pr switch to work the fuel pump but what else does it bypass?of course it dont run right but it starts right up consistently

i tried putting the car in limp mode and it will start eveytime I know it uses the oil pr switch to work the fuel pump but what else does it bypass?of course it dont run right but it starts right up consistently
It bypasses every sensor except TPS (and possibly CTS) If it never fails to start in limp home, I would be 80% confident that your memcal is bad, the info stored on it has gotten corrupted somehow.

i tried putting the car in limp mode and it will start eveytime I know it uses the oil pr switch to work the fuel pump but what else does it bypass?of course it dont run right but it starts right up consistently

As said the prom could be bad or may not be a match for you car or it could have a updated prom to correct running or starting problems.
Check with you dealer and have him run your vin no on his prom machine.
For the correct prom or for a updated one.
In them years GM had about 1K proms and updated proms.
Total nightmare. But a good dealer can sort it all out.
Good Luck

thank ya sir, It sounds worth a shot. I will go look for one tommorow. On emore ? for you guys when I have my scanner hook up and it starts the base pws hits like 6 and drops down to say 2.4 now when it wont it stays at 0 but reads rpm. should it show 6 or something even if it dont start ?Hope that makes sense. Ill try a memcal till then.

when I have my scanner hook up and it starts the base pws hits like 6 and drops down to say 2.4 now when it wont it stays at 0 but reads rpm. should it show 6 or something even if it dont start ?Hope that makes sense. Ill try a memcal till then.
Even if the engine doesn't start, if the ECM is pulsing the injectors you should be reading more than 0 for a BPW. If it is 0 then the ECM isn't allowing the injectors to fire..This could be a wiring problem, ECM/Memcal, ignition module/wiring and that's about it.

Alright 85 bucks for eprom wont have it till next week. So when Im trin to start it the scanner is reading rpm the noid light is blinkin but the scanner does not read the bpw, so if the eprom was corupt it may not have the right starting mode or not be switching to start mode at all. Does limp home bypass the prom and use backup fuel in the ecm or vise vera thanks in advance just trin to understand.

Tahnks for everyones help Someone put down a deposit on the car today and I have not replaced the prom yet. I did tell them it has a prob but it started for them today(must like em) They dont seem to relize the difficulty Ive had but I took the 3800 dollar ofer, The rest of the car is tip top so I wish em luck Till we meet again thanks Tony