KnuckleDragger

Bought an '89 GTA last Fall, and am just getting around to tuning it up. It ran like CRAP when I bought it. It turned out to be the Mass Airflow Sensor. I replaced it, and it ran a lot better. Immediately following that however - the check engine light came on and it throws the following codes. Any ideas?

Trouble codes: 1989 Pontiac Trans Am GTA
DTC - 51 Incorrect MEM-CAL
DTC - 44 Left bank O2 sensor error (lean condition indicated)
DTC - 42 Ignition bypass circuit error
DTC - 41 C³I Cam Sensor Signal error
DTC - 63 Right bank O2 sensor circuit error
DTC - 61 A/C system performance
DTC - 54 Fuel pump circuit low voltage
DTC - 52 Fuel cal-pak incorrect or missing

Tuned Performance

iTrader: (92)

Sounds like a bad ecm or a hypertech that's installed in the ecm.

KnuckleDragger

So - I'm new to Trans Ams. What is a hypertech? Any suggestions on where to start?

vetteoz

iTrader: (13)

An aftermarket " performance " chip for the car



Some of the codes you list not available for your car so the ECM or the memcal ( chip ) inside it would be the 1st suspect items
Try removing the memcal ( blue item in pic ) and replacing it to see if anything changes

KnuckleDragger

Where do I find the ECM?
Hmuch to replace the Mem-Cal?

I disconnected battery for quite awhile while I was working on other things. Hooked it back up, started the car... and the Service Engine Soon light came right back on. Someone told me to check the ground strap. I found one from the firewall that should have run to the passenger side head... not connected at all. I couldn't reach down to attach it... so I ran it from the firewall to the plenum.
Unhooked the battery... hooked it back up... still have SES light.

vetteoz

iTrader: (13)

button works

https://www.thirdgen.org/forums/dfi-...9-firbird.html

You don't replace it.
You remove it and reinstall it to confirm it is seated and being read correctly
The DTC - 52 ( cal-pak incorrect or missing ) you have is saying the ECM is not reading the memcal correctly ;
it may well actually be faulty , it also could not be seated in it's socket right

Has the car ever run properly since you had it?
Tell us the 4 letter ID code on the silver sticker on the memcal ; it may be the wrong tune for your engine

KnuckleDragger

No - the car did not run properly when I bought it in Oct 2013. I replaced the fuel filter, and the MAS. Now it runs like a champ... but the SES light is on.

I'll look into the ECM and chip Saturday then let you know what I find.

KnuckleDragger

The 4 digit code on the chip is 3516

I took it out, re-seated it... still have SES light.

Where is this supposed to be grounded? As I was looking over the engine - I noticed the ground strap from the firewall to the passenger side head wasn't even connected at the head. I reached down and felt the stud to attach it too, but I could barely get a nut started on it. There was no way to get a wrench on it to tighten it. Also - for the Hell of it - I ran another ground strap from the Driver side head to the firewall.

Still - SES is illuminated.

vetteoz

iTrader: (13)

Was after the 4 LETTER code ; should be APYU ?
( which is correct for your car )

Vader

Here's something to try:

Turn on the ignition, but don't engage the starter (I'm in this habit for several reasons);

Watch the SES lamp very closely when the ignition is first turned on. It should turn on for about ¼ second, then turn off for about ¼ second, then turn back on and remain on until the engine is started and running.

This SES lamp behavior is frequently termed the "SES Bounce" and if it doesn't occur, something is awry in the ECM or its wiring.

As for the grounding, you mentioned that you added a ground connection from the engine to the body, which is a good idea. Just verify that the smaller of the battery negative cables is also connected to the body and the larger connected to the engine.

This thread may be helpful:

https://www.thirdgen.org/forums/tech...-question.html

The ECM is supposed to operate in this manner:

Install the key and turn the ignition to RUN (not start). The SES lamp should light briefly, turn off briefly, then relight and remain lit until the engine is running. This flash, or "SES Bounce", indicates the ECM has run and passed some rudimentary self-diagnostics, like scanning for a valid EPROM, scanning for valid firmware PROMS, an input voltage test, I/O test (to see if any loads are connected), and some other internal systems tests. If there is a problem during this test, the lamp will remain off or flash once and remain off, depending upon the type of problem.

When the ECM is placed in Field Service Mode, the electric fan will operate continuously.

It seems that you may have an issue with the ECM. The first thing to do is disconnect the battery ground, expose the ECM, open the EPROM cover, and reseat the EPROM in its socket. Next, you should disconnect each header plug, inspect the contacts for damage, then reconnect them. Repeat the disconnection and reconnection a couple of times, and the contacts will tend to wipe clean the traces on the circuit card or connection pins. While you're there, verify a good ground connection to the ECM, since that is crucial.

Reassemble the ECM in place but do not replace the covers just yet. Start the engine and allow it to idle down normally. Once the engine is running, tap firmly on the ECM case with a couple of finger or lightweight screwdriver handle to see if any internal connections may be intermittent. If you detect a stumble, stall, or SES lamp as a result of the tapping, the ECM should come back out for further inspection.

Once that's accomplished, you may have solved your problems if the issue was poor connections from 15-year old contacts. Let's hope. If not, we're still here.

KnuckleDragger

Yes. Sorry. It is APYU.

KnuckleDragger

Vader - what do you mean disconnect each header plug? Is there an actual plug?
I'm totally lost on this car.

KnuckleDragger

Okay - so the SES light does do the one quick flash on and off, then remains lit. Once the car is started, the light goes off - but turns back on after about 5 seconds.

KnuckleDragger

I had 3 wires that broke out of the ECU harness, and went to the driver side head. nothing on the passenger side. I ran 2 brand new ground straps from the firewall to each head. Cleaned/roughed-up all contacts to ground.

When I first turn the key to start - the SES light does the "bounce" and remains on til the car is started. It then turns off - but comes right back on after about 5 seconds.

If I shut off the car, then turn key to on again - the SES light just remains lit. No bounce.

KnuckleDragger

So now - I can go to start the car... and it will run like total crap. Missing, spitting/sputtering. I can turn it off... pull the key out... put key in... re-start it, and it will fire right up and run like a champ.

Other times it's the complete opposite. It will fire right up and purr... but if I shut it off and start it again, it will spit/sputter and misfire.

ECU? Prom?

Tuned Performance

iTrader: (92)

Replied on your second related thread !

KnuckleDragger

Checking the codes with a paperclip... the only one that shows is 33.
I started this whole process by replacing the MAF sensor. Today I replaced the MAF sensor relay... still getting code 33.
Disconnecting the battery and removing the ECU fuse won't clear the code. As soon as I check again (without starting car) code 33 comes back.

vetteoz

iTrader: (13)

The code is for a fault SOMEWHERE in the system ; not that just the sensor or relay is faulty.
Could be a power / ground or wiring problem
Need to work through the diagnostic flow chart from the FSM for your car ( you have one don't you ? )

Typical DTC 33 chart here

http://www.chevythunder.com/maf_code_33.htm

KnuckleDragger

Oy! That looks daunting. Thanks man.

No - I do not have the FSM. I definitely need to invest in one. This car has been kicking my butt!

Vader

With a 33 code, it might be good to check the TPS voltage at closed throttle, and note the RPM at idle.

Another potential cause is a shorting/carboned MAF burnoff relay. You can actually remove the MAF burnoff relay and run the vehicle that way to check, but the relay will eventually need to be reinstalled to prevent a 36 error.

KnuckleDragger

How do I check TPS voltage?

Also - I've replaced the MAF power and burnoff relays.

keykey

Have you looked at the fuel pump relay? On my 88, the fuel pump relay sends the power to the two MAF-relays. When I bought my car it had several issues with sputtering/dying, non starts and code 36,33,34,44. It was the fuel pump relay and connector (I replaced relay+pigtail). And yes, the car started and ran even though they were bad, because they were "half-bad".

KnuckleDragger

Does this seem right to anyone else? The fuel pump relay sending power to the 2 MAF relays?

RBob

iTrader: (1)

On the '89, the fuel pump power feed goes to the MAF power relay coil. This is to activate the power relay to power up the MAF. The power for the MAF comes through the relay from the battery feed.

At key-off the MAF power relay switches to the NC set of contacts. The burnoff relay power is run through those contacts and onto the MAF. The burnoff power also goes right the burnoff terminal of the MAF sensor.

RBob.

keykey

Straight from the Factory Service Manual (there is a good wiring diagram showing the circuit on page 849 in the -88 FSM)! Also, the oil pressure switch is used as a backup, so obviously my pressure switch was also broken since the car had a no-start sometimes when the FP relay/harness acted up. I replaced both the OP switch and the relay + pigtail. I love the backup circuit thinking that GM had, now with both replaced I will probably never have to worry about the power feed to the fuel pump or MAF relays again as long as i own the car. The parts are cheap, I recommend replacing them anyway to know they´re in good working order!