rrwebster

I've got a ""stand alone" 1995 LT1 with 4l60e setup that was working beautifully.

While replacing the alternator, as I was removing the BAT connection my wrench slipped out of my hand falling onto the PCM; lots of sparks, many oh ****s later I got the new alternator on and started it up.

Idles around 1300 rpm, no change, no matter how long it runs. Trans is in limp mode.

The only thing that was shorting (BAT to PCM was the outside case)

I do have 12 volts at pin E on the transmission feed.

Pulling the MAF Connector doesn't really change anything.


Yes, I do know better than to not disconnect the battery. This setup works just fine normally, I have in another older car as well.

I can't use my scanner on it, not sure it it's my connection or the cable.

What might I have fried?

Injuneer

What DLC setup are you using - 12-pin or 16-pin? If 16-pin, do you have 12 V on pin 16?

rrwebster

16 pin power at 16. 2 grounds and the data feed. Using a 1995 only cable.

rrwebster

I just found this on another thread. is there any truth in this? I am not running o2 sensors, should I be?


<<<there is no such thing as limp mode. you have SES for some reason... probably O2 sensor related if you are getting 10 mpg. figure out which one is bad and replace it... yes it is that easy. the reason you are getting bad gas mileage is b/c your car is staying in open loop so the computer isnt allowed to make the necessary adjustments from the feedback available by the O2 sensors.>>>

rrwebster

Okay, I can scan again. went directly to pin 30 on the blue plug of the PCM and it's good.

I have a

48 Mass Airflow system Failure
41 EST Open
22 throttle position low

EST open I've not heard of... Will work on the others

DrewHMS97SS

TPS is relating to the voltage being sent by the sensor. Do you have an aftermarket 58MM tb? It is not uncommon to need to notch holes in the TPS to set the sensor within spec. Take a measurement from the blue wire coming from the TPS. I believe the LT1 was originally set at .63 (I'll measure mine tonight).

Fred had some good insight here: https://www.camaroz28.com/forums/lt1...stment-833907/

For the MAF, is it stock? If stock, are the screens in place? If not stock, what is it? Did you check the wires for melting? Do you have an oiled air filter?

DrewHMS97SS

Stolen from Camaro Zone:
Notes DTC 41 Chart Ignition Control Circuit
Ignition System Wiring Diagram

Circuit Description:

The ignition system provides two timing inputs to the ECM, high resolution (360 pulses per crankshaft revolution) and low resolution (4 pulses per crankshaft revolution). The ECM uses these two reference pulses to determine individual ignition spark timing for each cylinder.

Once the ECM calculates ignition timing, the timing signal will be sent to the ignition coil module on the IC circuit. Each timing pulse received by the ignition coil module, on the IC circuit, will trigger the ignition coil module to operate the ignition coil. Secondary ignition voltage is induced and is then sent to the distributor for distribution to each spark plug.

The IC signal voltage ranges from about 0.5 volt to 4.5 volts.

If a DTC 41 is detected, the ECM will disable the fuel injectors to prevent flooding of the engine. DTC 41 will set if the IC circuit problem occurs during cranking.

Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.


DTC 41 will set if:
Voltage on CKT 423 exceeds 4.6 volts.
Engine speed is less than 1500 RPM.
Without the engine running or cranking there would be no voltage present on the IC line.
This check determines if the IC signal from the ECM is available at the ignition coil module. The IC circuit voltage should be between about 0.5 and 4.5 volts.
The remaining tests begin to check that the ignition coil module circuitry is OK.
If all wiring and connections are OK, check the ignition coil or the ignition coil voltage supply.
Diagnostic Aids:

Since the ignition coil module gets its power from the coil, check the ignition feed circuit to the ignition coil for opens.

rrwebster

48 Mass Airflow system Failure Forgot I had stuck and older one on there... put the original back.. Fixed
41 EST Open I Had bought an ICM from Amazon for $10, stole the one off the LT1 in one of my corvette's (you get what you pay for)Fixed

22 throttle position low, again, stole one off one of the corvettes, Fixed


Back to shifting again! Thanks guys... BTW That power on #16 with my cab;e... it will go either way... I needed the jumper and forgot to put it back and it still worked.

Injuneer

Depends on whether your scanner needs the 12 V pin as a power supply. Some do, some don't.