Datamaster scan questions
Thread Starter
Registered User
Joined: Nov 2002
Posts: 1,332
From: Louisville KY
Car missing, scanned it
I just scanned my car at idle, and revving (no laptop yet, had to hook it up to comp in the garage). It takes longer to start the car than used to, especially when it has sat for a while, it will occasionally miss, at first was just higher rpms, now will do it intermittently no matter if idling, driving, accelerating, etc. My gas mileage is also down to about 200-215 miles per tank before empty. The opti has over 120k on it, so I assume it is the problem since at the end of summer I did a tune up with new MSD wires, coil, and NGK plugs. The SES light is not always on, but rather comes on and off occasionally when driving. I scanned it once on 1/23 and again today. The DTC codes on jan 23 were; DTC 16 - Low-res fail, DTC 43 - ESC fail, and DTC 77 - Fan 1 fault. Today it is showing the same codes except 16, the only thing I've done to the car since Jan 23 was replace the battery.
What does this mean, and what is causing my miss? The opti?
I can email both datamaster scans if anyone can help with my diagnosis.
Thanks!
What does this mean, and what is causing my miss? The opti?
I can email both datamaster scans if anyone can help with my diagnosis.
Thanks!
Last edited by kgkern01; Mar 15, 2006 at 08:19 PM.
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Joined: Nov 1998
Posts: 71,094
From: Hell was full so they sent me to NJ
Re: Datamaster scan questions
You need to look up the LT1 specific codes on the list that Shoebox has on his website... not a good idea to use generic code lists.
DTC 43 = Knock Sensor (KS) circuit
Your knock sensor is dead or the wire is off of damaged. You are getting continuous knock retard, because without the knock sensor, the PCM defaults to internal tables that apply a lot of knock retard to protect the engine. Can't be helping you.
DTC 77 - Cooling fan relay control circuit
One of you cooling fan relays is bad. Needs to be replaced. As a result, one of yuor fans may not be working.
DTC 16 - Distributor ignition system (low resolution pulse)
That's low of one of the critical signals from the Opti. But if you have it, and the engine is running, its a "stored" code. The PCM shuts down the fuel system if it can't find the low res pulse from the Opt. It is not unusual to see this as a stored code. I think sometimes the PCM has a problem finding the pulse signal on startup.... and you are having delayed startup. Might be worth, as a minimum, checking the Opti wiring harness connectors for corrosion.
Hard starting can be tied to a couple things:
Faulty coolant temp sensor. You should be able to look at your data logs and see if the coolant temps look correct.
Loss of fuel pressure after prime. This can be caused by a damaged fuel pressure regulator, a faulty check valve in the fuel pump, or leaking injectors. Check with a fuel pressure gauge, and see how long it take for the pressure to drop off after shutdown.
If its dropping fast, pull the vacuum line off the fuel pressure regulator vacuum line and look, smell for fuel.... there shouldn't be any. You can pull the fuel rail up, pressure the fuel system and look for dripping injectors.
If both those are OK, could be the fuel pump check valve.
You might also want to check the fuel pressure at WOT/max load to be sure the pump and filter are healthy, and can hold the pressure above 40psi.
Beyond that, misfires can come from injectors, the parts of the ignition you haven't replaced (ICM), corroded wire terminals on the Opti, heat soak of the ICM or Opti optical electronics, etc. Misfires cause the PCM to add fuel the engine doesn't need, to the gas mileage falls off.
If you can e-mail your DataMaster files in ".csv" format (there is an "export as .csv" option), I can take a look at it. I only ask that you be patient, because sometimes it takes me a while to get to them. Be sure to check your .csv files before you mail them. Often people do the "export" and it only sends the first line, not the full file.
DTC 43 = Knock Sensor (KS) circuit
Your knock sensor is dead or the wire is off of damaged. You are getting continuous knock retard, because without the knock sensor, the PCM defaults to internal tables that apply a lot of knock retard to protect the engine. Can't be helping you.
DTC 77 - Cooling fan relay control circuit
One of you cooling fan relays is bad. Needs to be replaced. As a result, one of yuor fans may not be working.
DTC 16 - Distributor ignition system (low resolution pulse)
That's low of one of the critical signals from the Opti. But if you have it, and the engine is running, its a "stored" code. The PCM shuts down the fuel system if it can't find the low res pulse from the Opt. It is not unusual to see this as a stored code. I think sometimes the PCM has a problem finding the pulse signal on startup.... and you are having delayed startup. Might be worth, as a minimum, checking the Opti wiring harness connectors for corrosion.
Hard starting can be tied to a couple things:
Faulty coolant temp sensor. You should be able to look at your data logs and see if the coolant temps look correct.
Loss of fuel pressure after prime. This can be caused by a damaged fuel pressure regulator, a faulty check valve in the fuel pump, or leaking injectors. Check with a fuel pressure gauge, and see how long it take for the pressure to drop off after shutdown.
If its dropping fast, pull the vacuum line off the fuel pressure regulator vacuum line and look, smell for fuel.... there shouldn't be any. You can pull the fuel rail up, pressure the fuel system and look for dripping injectors.
If both those are OK, could be the fuel pump check valve.
You might also want to check the fuel pressure at WOT/max load to be sure the pump and filter are healthy, and can hold the pressure above 40psi.
Beyond that, misfires can come from injectors, the parts of the ignition you haven't replaced (ICM), corroded wire terminals on the Opti, heat soak of the ICM or Opti optical electronics, etc. Misfires cause the PCM to add fuel the engine doesn't need, to the gas mileage falls off.
If you can e-mail your DataMaster files in ".csv" format (there is an "export as .csv" option), I can take a look at it. I only ask that you be patient, because sometimes it takes me a while to get to them. Be sure to check your .csv files before you mail them. Often people do the "export" and it only sends the first line, not the full file.
Thread Starter
Registered User
Joined: Nov 2002
Posts: 1,332
From: Louisville KY
Re: Datamaster scan questions
Well I haven't rescanned the car yet, forgot to bring the cable over today when I was working on the car. However lately it has gotten bad, smelling more like gas (i dont have cats), backfiring on release of gas when shifting, and loud ticking coming from pass side back of engine. Am waiting for my opti to come in so decided to just replace the pass side back plug to see what happens and to inspect the old one. Well the old one was black, but not sooty, more like oily and it smelled like gas.
So I'm thinkin its either:
1. bad injector
2. bad valve/seal/lifter, etc.
3. Opti is bad on that cylinder
4. Worst case, blowby on that cylinder
5. Other....
What are some opinions?
So I'm thinkin its either:
1. bad injector
2. bad valve/seal/lifter, etc.
3. Opti is bad on that cylinder
4. Worst case, blowby on that cylinder
5. Other....
What are some opinions?
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