1994 Park Avenue Ultra Codes

[happyreefer]

I'm new to the Buick Park Ave, I bought this car with 93K on the odometer and a check engine light on.

Just got back from Pep Boys and had the codes read from my Park Avenue. here is what they gave me. any help would be apprecieated.

they first read the codes and got all these
P0640
P0171
P0406
P0401
P0740

then cleared all codes and drove the car and re read the codes. only one came back. this one.

P0640


Gary

[HotZ28]

DTC P0640 Invalid Code
DTC P0171 Fuel Trim System Lean Bank 1
DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient
DTC P0406 Exhaust Gas Recirculation Sensor A Circuit High
DTC P0740 TCC Enable Solenoid Circuit Electrical

[happyreefer]

You say that the P0640 Code was invalid, but the Service Tech said this one was there before resetting the codes, and then was the only one that came back after driving the car.

The Tech told me the P0640 was "Quad Driver Module QDM-1 Fault".

Is this correct? searching on here and throughout the web has really got me no where.

"Service Engine Soon" light comes on only after i start driving. I is off when I start the car and only comes on approximate 1 mile after coming up to 35mph. mph is approximate, does seem to be exact every time, same with distance. it stays off even when just at idle.

Car seems to drive ok, but Fuel mileage seems to be lower than expected. I am not a heavy foot and after just a couple of tanks, MPG seems to be around 15-16. I was expecting at least 20. I live in San Diego and commute 30mile one way to work, 95% interstate at around 70mph. I am thinking this Check engine light is somehow connected to the emissions system and is affecting mpg in some way.

If i was to buy my own Scan Tool, what would be the best bet. i know that these few years in the Park Avenue have a hard time being read.

Any Ideas? My plan is to take it to an actual Buick Dealer and have them look at it, but i am not one just to throw parts at a problem until i solve it.

Gary

[HotZ28]

Obviously, you have a failing EGR valve. You may try cleaning it, if that don't work, replace it. FYI, the same info below applies to your 94-PA.

DTC P0640 - Invalid Diagnostic Trouble Code This vehicle does NOT generate this Trouble Code.
There is one particular after market scan tool that still has not been updated and generates these and other Invalid DTC codes.
The work-around is to use the DTC description, and find a code that matches it. A number of technicians have used Code P1640 (close match to P0640) when the description matches a Quad Driver 1 Problem.
This code points to a Quad driver. They are like a circuit breaker inside the PCM that can control up to four different outputs on each one. Chances are there is a shorted solenoid somewhere. You need a service manual to determine what solenoids are involved on the quad driver. Then unplug each one to see if the problem goes away. There is an actual test in book for this code that will point you in the right direction.

Source: http://autorepair.about.com/library/a/1f/bl518f.htm

[happyreefer]

Ok, so i replaced my EGR Valve and i am still getting the Service Engine Soon light.

I guess its time to buy a service manual. Once I locate a service manual i will trouble shoot more as per the above post and follow up with my out come.

HOTZ28, thanks for your support.

Gary

[HotZ28]

I assume you cleared the code after changing the the EGR? The EGR solenoids are activated by Quad drivers which can be damaged over time by a shorted circuit in the solenoid. If this is the case, a new or rebuilt PCM may be needed. BTW, 94-95 model PCM's were failure prone.

[happyreefer]

OK, so i admit, i did not reset the codes initially, but after i read your post I went out and removed the Neg Battery Terminal for a couple of minutes to reset the computer.

Re test drove the car and Service Engine Soon light came on still. I am getting ready to make a 160 mile drive back to San Diego and I will be checking MPG to see if i notice any change.

I will research PCM's for this year. Am i correct that these are also called ECM too? A quick internet search looks like 150ish for a reman PCM/ECM, but i will not throw anymore parts at it until I am sure i know what the problem is.

I am still going to get the service manual once I return home.

Thanks for the continued Support
Gary

[procaddytech]

Use P1640 diagnostics. The PCM WILL illuminate the MIL (Service Engine Soon) with a current DTC P1640 set.
Quad Driver #1 Circuits:

P0740, TCC apply solenoid circuit is a circuit to focus on. With a current DTC P0740 set, the PCM will not allow 4th gear operation. DTC P0740 DOES NOT illuminate the MIL (Service Engine Soon).

[happyreefer]

Drove the 160 mile return trip to San Diego after replacing my EGR Valve. MPG seems to be the same with no increase.

Halfway through the trip, i notice higher RPM's while at highway speed. Got home and checked all vacuum lines. I noticed many of the vacuum fittings dry rotted, so i replace all that seemed bad. Reset Codes again by disconnecting the Negative Battery Terminal for a couple of minutes. and took for a test drive. Service Engine Soon still comes on about 2 miles of driving. RPM's did return to normal highway speed RPM's after fixing the vacuum leaks.

procaddytech, I am looking at your diagrams and it looks as if the Quad Driver 1 fault could be the: Torque Converter Solenoid, Boost Control, or the Evap Canister Purge?. Not really sure where to go from here.

Gary

[HotZ28]

Originally Posted by happyreefer

Service Engine Soon still comes on about 2 miles of driving. RPM's did return to normal highway speed RPM's after fixing the vacuum leaks.

Before we go any further, we need the current code.

[happyreefer]

What Code Reader can I buy to read the codes properly. The autozone guys said California Autozones wont read the codes.

I was in AZ over the weekend and that's where I had the Pep Boys Read the codes for me. they didn't charge anything.

Thanks for the help so far, i dont know when i will get the codes read unless i go over to the Buick dealer (they want $105.00). that's why i should just buy a code reader myself, I work on enough cars that it would probably pay off.

Gary

[procaddytech]

Any one of those solenoids or its circuit could could have a fault causing the quad driver to stop operating to protect itself. Or it could be the quad driver itself. Like HotZ28 says, the current code is needed. Looking at the P1640 flow chart, and the codes you originally posted, the TCC solenoid is the only thing left. Vacuum leaks will cause a P0171, the P401 and P406 may have been fixed with the new EGR valve.
You will need a scanner capable of allowing you to command solenoids on and off. Do you have 4th gear all of the time? No 4th and no TCC will cause terrible gas mileage. A DTC is really needed so we aren't chasing our tails. I will put up the Quad driver chart (P1640) shortly.

[happyreefer]

I believe I am getting all my gears now that I fixed the Vacuum leaks. I commute 30 Miles each way for work. I usually keep it about 70mph and my rpm's are right around 2K. when I had the vacuum leaks rpm's were 3K+ at 75-80mph.

Not sure how to check for my torque convert locking and what speed it locks at. I will be looking for a Scan Tool that is able to scan the 94 Park Ave Ultra with the 16pin connector.

Gary

[HotZ28]

Originally Posted by happyreefer

I will be looking for a Scan Tool that is able to scan the 94 Park Ave Ultra with the 16pin connector.

Gary

Click Here

[happyreefer]

That scanner seems like the reviews are hit and miss.. but overall seems like it will work well for the average driveway mechanic.

It has been ordered and I should have it on Wednesday sometime.