Advice on what to do to resolve codes

[wachuku]

Problem: '97 STS seemed fine; now it won't start.

Background: Over the course of about a week, the car's "health" deteriorated as follows: (i) running fine; (ii) rough start; (iii) rough start and won't reach RPM above ~2000 RPM without restart, then run fine; (iv) rough start and stalling every 100 ft; (v) won't start.

Prior to all this, I inadvertently "deep cycled" the battery with the engine off to the point where I needed to jump-start the car. Symptoms (iv) and (v) didn't appear until this weekend, so I was working under the assumption that I wrecked the battery, it wasn't holding a good charge, and was causing rough starts and maybe also computer glitches that were followed by seemingly perfect operation after restarting with more charge in the battery. During this time I was also monitoring voltage which would always display as 13.7 to 14.4 shortly after startup, so I assumed I didn't torch the alt.

In the process of getting a new battery this weekend however, the car exhibited symptoms (iv) and (v). Now although the car turns over nicely, it won't start at all, even with a new battery and a jump.

Here are the codes (all "history"):

• PCM
  • P0603 - Control Module Long Term Memory Reset
• IPC
  • B1552 - Keep Alive Memory (KAM) Error
• SDM
  • B1159 - Loss of Serial Data-Key Not Received
  • B1160 - Loss of Serial Data - VIN Not Received
  • B1163 - Loss of Serial Data-No Lamp Response
  • U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)
• TCS
  • U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)
• PZM
  • U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)
• IRC
  • U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)
  • U1064 - Loss of Communications with DIM
  • U1096 - Loss of Communications with IPC

I run codes routinely, and I know I didn't have any of these prior to deep-cycling the battery. On the other hand though, maybe in light of "U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)", the battery problem is a "red herring". Is there an easy way to check the integrity of serial data line communications? I'm not $o $ure I want to $eek the $ervices of a techII if I can avoid. I hope these codes don't mean a reprogramming of some sort will be required.

====================================

For anyone who might be interested in even more info, below are the codes I received during the middle of last week, when the car seemed run run perfectly if either of the following two startup conditions were met:

• not long time off (e.g. less than over night) -- run perfectly
• restart after start and idle for 30-60 sec -- run perfectly

Codes when the car would run (all "history"):

• PCM
  • P1604 - Loss of IPC Serial Data
  • P1605 - Loss of HVAC Serial Data
  • P1610 - Loss of PZM Serial Data
  • P1626 - Theft Deterrent Fuel Enable Signal Not Received
• IPC
  • B1552 - Keep Alive Memory (KAM) Error
  • B1910 - Generator L-Terminal Open Circuit
  • U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)
• ACM
  • B1983 - Device Power Circuit Low
  • U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)
  • U1096 - Loss of Communications with IPC
• SDM
  • B1159 - Loss of Serial Data-Key Not Received
  • B1160 - Loss of Serial Data - VIN Not Received
  • B1163 - Loss of Serial Data-No Lamp Response
  • U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)
• IRC
  • U1255 - Class 2 Communication Malfunction (Serial Data Line Malfunction)
  • U1064 - Loss of Communications with DIM
  • U1096 - Loss of Communications with IPC

====================================

One difference between when the car would and would not run is the emergence of the code "PCM P0603 - Control Module Long Term Memory Reset". Is this the likely culprit, and if so, is there a way to fix it?

Hoping for some insights.

[N*Caddy]

All the symptoms will point me to a gas issue (like no gas pressure = bad pump) but the codes are very clear about a bug with the serial data line.
P0603, B1552, B1983 and even U1255 are from the deep battery cycle, but all the rest are more than clear about the data line problem.
Another thing, you can have all this strange modules communication errors just because of a low voltage. This is where I would start first, try a known good battery.

[dkozloski]

Dittto on the battery. It sounds like a battery issue but unless the battery is old I'd try about a day on a charger and a load test before I bought another. Discharging a battery completely dead won't hurt it unless you let it sit around dead for a month or more.

[Necrosan]

Battery.

[ewill3rd]

I am sort of confused.
It looks like you put the battery in already and now it cranks but won't start, is that right?

Does the cluster light up when you turn the key on and display accurate data (like fuel level)?
If so I'd almost be willing to ignore all the communication codes. Those could have been set by the dead/dying, or disconnected and reconnected battery.

Step 1: clear all the codes
Step 2: Try to start the car
Step 3: Tell us what is happening right now

The rest is just confusing.

[egheorghe]

i have the same code U1255 as current. I don't know how to clean it. I noticed that the radio stations memorised on my radio disappeared every couple of days, or right after i used another source (CD, Tape). Does it have anything to do with the code U1255? The battery one yr old.
Thank you!

[wachuku]

‘Preciate the responses fellas.

I cleared the codes.

The car cranks but still doesn’t start, nor does it produce any codes. So I guess the car is in the clear for whichever codes -- if any -- can be produced during cranking.

After I cleared the codes it seemed like the car was going to start right up -- for about a quarter second, and then it stalled. My best description is it seems like either no gas or no spark.

The driver’s analog control cluster lights up and indicates 3/4 tank of gas which I believe is accurate. I pushed on the rear of the car and heard liquid sloshing. There are no obvious leaks.

I did remove the drivers analog control panel recently, but the car seemed to operate perfectly immediately after I re-installed the cluster. Moreover I was careful not to turn the car on while the cluster was removed, because I didn't know what computer glitches might be generated with the odometer disconnected and I didn't want to find out "the hard way". Should I be double checking the cluster connections (remove dash again)?

Last summer I replaced the fuel filter at the 100,000 mile mark, and two summers ago I replaced the fuel pressure regulator (FPR) -- I think the symptoms with the FPR were that the car seemed to run rich, especially at start-up. Could a faulty FPR also cause a lack of gas?

To reiterate, symptoms began by the car not responding to throttle immediately after start-up. The fix was simply to restart. Then all of a sudden -- and for a very short period of time -- the car started stalling every 100 ft or so, similar to how a car might behave when an alt blows and the battery is on its last leg. Now the car won’t start at all, in spite of a new battery that was also supplemented by a jump from another idling vehicle. (It turns over just fine, but won't "catch").

The thing just "fell off a cliff". Saturday night I drove with my GF to a fund-raiser and everything seemed perfect -- other than the usual start-up problem, which, at the time, I assumed was due to a low battery charge. Very near to home on the way back however, it all of a sudden started stalling all the time. Luckily I go it home, and now it won't start at all.

Any more thoughts?

[wachuku]

egheorghe I've messed around a lot with my "radio" (which I like to call head-unit), and although I can't provide a definitive answer, if I remember correctly I believe that yes radio anomilies can result in a U1255 code. I believe I get such a code if for example I operate the car with the radio removed. Maybe your radio has a bad internal connection or maybe the electrical connector is loose.

Perhaps the others can offer further insights.

[wachuku]

...Just re-read the posts. Any further comments on the pump suspicions of N*Caddy? Does a bad pump produce codes? Are there any simple ways to check fuel pump integrity? Where is it on a '97 STS? Does a failing pump result in the progressive/intermittent symptoms of the type I've described?

I don't consider myself a person capable of diagnosing issues with these cars, but the suspicions of N*Caddy seem to me like a good place to focus.

[ewill3rd]

A bad pump will not produce codes. At this point you need to perform some basic checks.
I'd start with fuel pressure. Do you have (or can you get) a fuel pressure gage?
I think you should see about 45 psi with the pump running (while cranking).
You sure the car has gas in it? Sometimes the gage can be messed up and make you think you have gas when you don't. In either of those cases it would be time to drop the fuel tank to fix it.
Next would be checking for spark, any parts store will have an ST-125 spark tester. Those are made to check GM HEI systems. An easy task on that engine.

[N*Caddy]

Gheorghe,
Have you removed the head unit (radio) from the car, or have you done any under dashboard work? The U code is network failure. I don’t remember the pins (I have the schematics somewhere) but start by making sure the connector is plugged properly in the back of the HU. If all tight you might have a failing HU (the chip). Not a big issue, you can find a replacement HU with less than $50 on E-bay, just make sure is for your year and model (although they look the same they are TOTALLY different inside).

As for the fuel pump issue, yes the pump will not trigger any code but will get the service engine soon light on. The simplest way to check the pump is just to push the fuel line service valve (Caution! high pressure gas, no flames, protect your eyes). If sprays with key in ON position (I mean really really sprays) then the pump is likely to be OK.

[wachuku]

Thank you very much ewill3rd and N*Caddy for your follow-up responses to this post; they've been invaluable for helping me hone in on the problem.

Following up on what you guys have been pointing towards -- in particular, "no gas" problems -- I did some research on my own. I looked at components in addition to fuel pumps that could cause problems similar to those I'm experiencing, and one possibility seems to be the fuel pressure regulator (FPR). I have heard they can fail in numerous ways, one being to fail open so that there is too much back pressure causing poor acceleration or even worse, no start (apparently the FPR is on the return side of the fuel line). Such would describe my symptoms; for a while I experienced poor acceleration at startup, progressing to no startup at all. Also, if a FPR fails open the car can seem to catch very shortly and then die, which is exactly what mine did last time I tried to start it. Furthermore, some, but not all, people contend that fuel pumps do not exhibit symptom prior to failure; instead they contend the pump will be perfectly fine and then fail, which does not describe my situation. Apparently FPRs on the other hand can exhibit intermittent symptoms similar to those I've experienced prior to all out failures.

Here's what I found out last night:

• cheapest fuel line pressure tester I can easily get is ~$50
• Delco FPR ~$60
• fuel pump ~$300
• I think a spark tester should be cheap?

As of last night, I was almost inclined to test for spark because it's cheap to do (which I suspect will be OK, but who knows for sure), and then assuming spark is OK, test for fuel pressure in the form of throwing a new FPR at the system, since a FPR costs about the same as a pressure gauge. Then if a new FPR didn't work, I'd move to fuel pump -- but such involves assumptions.

In light of N*Caddy's comments though, maybe I don't need to make any assumptions:

yes the pump will not trigger any code but will get the service engine soon light on. The simplest way to check the pump is just to push the fuel line service valve (Caution! high pressure gas, no flames, protect your eyes). If sprays with key in ON position (I mean really really sprays) then the pump is likely to be OK.

I wasn't getting a service engine soon light (and the light works), so perhaps the pump is good.

Can I effectively perform the test on the fuel pump suggested by N*Caddy even if the FPR is malfunctioning (and can anyone guide me to the location of the fuel line service valve)?

If so I think I should perform the test on the fuel pump suggested by N*Caddy, and if gas sprays, I'm inclined to test for spark, which I suspect will be fine, and then replace the FPR.

Does such seem like a reasonable plan?

[N*Caddy]

Not sure about the FPR thing (never experienced one), but I guess if the FPR sends the gas back in to the tank, the pressure will be low at the valve. The valve is just at the end of the fuel line (i.e. under the beauty cover front bank, driver side, cylinder 8 - top right from the injector). The spray test will just tell if you have gas, how good is the pressure … not very accurate (you got to have an eye for it something like … yeah looks like is about right). The best analogy is trying to measure the tire pressure by the noise the air makes when you push in the tire valve.
Here are some pictures of the two fuel lines available on ’97 STS:
Stainless steel (I hope you have this one)
Nylon (change-it as soon as you can, is a recall for it).
The service valve is (looking to the first picture) in the right side of the picture (about 1/4 from the bottom), looks like a tire valve just bigger. As for the second picture is about in the same location.
Here is a picture with both fuel lines removed from the car, the easiest to spot valve is on the metal one (the thing in the tip).

[ewill3rd]

The main FPR failure is a leak to the intake through the small vacuum line that regulates pressure.
I have never seen a regulator fail in a way that causes a loss of fuel pressure that I can recall.

To check the FPR you can simply remove the vacuum hose and crank the engine, watch for fuel leaking out.
FPR can cause a hard start, stalling, black smoke, and a poor engine idle at times.
It should not be responsible for a "no start" condition unless the engine is flooded.
You can remove the FPR vacuum line and hold the gas pedal to the floor, if you can get it started and fuel is leaking out. Replacing the FPR without any testing would be like throwing money out the window.
Testing spark is a good idea.
Be sure to keep us posted.

[wachuku]

Update 1-JUL-2008

Thank you again to N*Caddy and ewill3rd for your invaluable help thus far.

I looked at the pics of the fuel rails posted by N*Caddy. The fuel rail on my car is metal. It seems that the previous owner did a nice job of keeping everything up to date. (I know he had an extended warranty, and he may have been a stickler).

I checked for fuel spray from the fuel rail with its Schrader valve open. Fuel sprayed -- but whether it was "really really spraying", I don't know.

I bought a High Energy Ignition spark tester as suggested by ewill3rd. I tested all front-bank plug wires plus the outside wires on the rear bank. All appeared to spark without missing, so I concluded that lack of spark is not causing the problem. (Even in the unlikely event that the two untested inner wires on the rear bank were bad, I'd imagine the engine would still start).

I listened for pump whirring in the gas tank after turning ignition to "on" (with engine off). Whirring is present for a brief time so pump fuse is not causing the problem.

However, if I understand correctly, there are two fuel pump relays, and I wonder if "ignition on" test engages both or just one, and whether I need to run a test on a second relay?

Next I replaced the fuel filter. After this the car started right up! I went inside to wash-up, figuring I'd let the battery charge a little while idling before a test drive. As soon as I touched the gas pedal upon returning though, the car started idling rough, and after about two minutes it stalled. There appeared to be no codes not related to stall.

Now it behaves as it did prior to installing the new fuel filter: it turns over but won't start.

I bought a fuel pressure gauge as suggested by ewill3rd. 10 psi after key to on position; 10 psi while turning over trying to start. (According to Haynes, 97 N* pressure should be 48-55 psi; I tried previously without success to get a "real" manual, what are they called, Helm?)

If replacing fuel pump weren't expensive ($300 part), seemingly difficult ('97 means drop tank) and potentially dangerous (novice meets gasoline), I'd replace the pump. But because of the expense and difficulty of replacing the pump, I want to rule out all other possibilities before attempting.

Could something related to failure of one of two pump relays cause the 10 psi issue, and if so can I test for such?

Also, three different sources have indicated a bad fuel pressure regular (FRP) can cause low pressure -- this by failing open and allowing fuel to return back to tank too easily. (Something different from a leaking diaphragm). A suggested test for FRP fail open is to restrict the fuel return line while monitoring pressure with gauge, but I've heard this can damage the return line.

Is there any way to test for a FRP failed open?

(I don't think removing the FPR vacuum line is the correct test for FPR failed open).

In light of cost & difficulty of fuel pump replacement, I'm contemplating "throwing a FPR at it". I do not want to try and drop the tank and replace the pump only to find that pump wasn't causing the problem.

The car appears to hold what little pressure is in the fuel line -- for example, if I test at night and remove something from fuel line the next morning, fuel spays all over -- so I don't think there's a leak anywhere.

Any thoughts are welcome.

In the mean time I'll start familiarizing myself with what I suspect will be my next endeavor -- fuel pump replacement instructions:
http://www.cadillacforums.com/forums...tructions.html (Fuel pump replacement instructions)


(By the way, N*Caddy if you see this, I just got a PM you sent ~ a month ago about prices of shocks. I guess I'm not very internet savvy, but I appreciate the message and I hope it all worked out for you).