2002 Oldsmobile Silhouette Gauges turn off and on among oth

I am beginning to think that my catalytic converter needs replaced as well as the downstream o2 sensor. I have a P0420 fault and both o2 sensors read the same number. Usually sensor 1 reads something then a split second later sensor 2 reads what sensor 1 did. I am wondering if this is causing the engine to get warmer than usual thus causing the PCM to overheat and cause the above problems???

Part of my reasoning is the fact that I just (back in march) had the manifold gaskets replaced as they were blown out and leaking. Job I would have done myself but it happend the day before my wife was going to go on a mexican riviera cruise so I dropped it off. We dropped it off because it overheated and stopped running. So we waited till it cooled off some and then drove it to the shop.

*edit I should add that the hotter it becomes outside the more often the powering off and on happens. If its in the 70's it doesnt happen until 30-40 miles down the road. When its in the 90's like today it happens within 5 miles down the road and then goes off for 30 seconds or so then back on for 15 then back off for 30 etc etc. I am afraid im gonna burn another ignition switch up if I keep driving it in this weather.

First step on these is to scan with a GM capable tool, this will read B and U codes the generic scanners cant read, my money is on the BCM, but scan first, buy parts later.
P0420 is the catalyst efficiency low code, can be a bad cat and or no switching of the upstream O2 sensor, this sensor switches constantly between rich and lean, when it doesn't do this it's one or the other or both... bang on the converter to check for rattles, this will indicate a broken converter bed. Pieces get trapped in pipes and mufflers, this must be cleared out to function.

I have already replaced the BCM and it did not fix it.

OMG I dont know if you saw the previous message but I was wrong. I didnt realize there was an enhanced system I had to go into on my scanner to read the B and U codes. I did not get any B codes but I did get some U. In the enhanced I got

P1626 Theft Deterrent System - Fuel Enable Circuit
U1040 Loss of Class 2 Communications with ABS
U1096 Loss of Communications with IPC
U1300 Class 2 Short to Ground

I will do some research on these while I await a new response.

Could my problem be the PK3/antitheft security module going bad (the one that goes around the tumbler and sits on the side of the ignition switch)? I wiggle the keys when this happens and it has no affect whatsoever so I am assuming its not the tumblers. If it is the theftlock where would I be able to find one to replace it as I am having a hard time finding one. I should also mention this is the stock security system GM installed. I know it cant be the remote batteries because my wife doesnt even use her remote on the van. It hasnt been on her key chain in a few years.

if that is the case it would be cheaper for me to install a remote car starter than to replace this thing.

as for the o2 sensor it is constantly switching between .06 to .95 volts. So once I get this other problem fixed I will install a new cat but I am more interested in the first problem.

Trace the wire from terminal 2, on the connector, it is shorted to ground, or the terminal at Pin 5 is shorted to power, 2 is the class 2 line and 5 is the class 2 ground. Conditions for Running the DTCs  Voltage supplied to the module is in the normal operating voltage range.  The vehicle power mode requires serial data communication to occur. Conditions for Setting the DTCs  No valid messages are detected on the class 2 serial data circuit.  The voltage level detected on the class 2 serial data circuit is under one of the following conditions:  Always high  Always low  The above conditions are met for approximately 3 seconds. Action Taken When the DTCs Sets  The module inhibits the setting of all other class 2 DTCs.  The module uses default values for all parameters received on the class 2 serial data circuit. Conditions for Clearing the DTC  A current DTC clears when the malfunction is no longer present.  A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction. Diagnostic Aids  These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to Scan Tool Does Not Communicate with Class 2 Device .  An intermittent condition is likely to be caused by a short or an open on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to Scan Tool Does Not Communicate with Class 2 Device . SCAN TOOL DOES NOT POWER UP Circuit Description The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following:  Scan tool power battery positive voltage at terminal 16.  Scan tool power ground at terminal 4.  Common signal ground at terminal 5. The scan tool will power up with the ignition Off. Some modules however, will not communicate unless the ignition is On and the power mode master (PMM) module sends the appropriate power mode message. Test Description The number below refers to the step number on the diagnostic table. 4. If the battery positive voltage and ground circuits of the DLC are functioning properly. The malfunction must be due to the scan tool. Fig. 11: Scan Tool Does Not Power Up Courtesy of GENERAL MOTORS CORP. SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE Circuit Description Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the DLC allows communication with the modules for diagnostic purposes. Diagnostic trouble codes (DTCs) may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory. Diagnostic Aids  If a short to B+ is present, a history U1301 or U1305 will set in the modules. Refer to DTC U1300, U1301, or U1305 (Generic Short DTC) .  If a short to ground is present, a history U1300 or U1305 will set in the modules. Refer to DTC U1300, U1301, or U1305 (Generic Short DTC) .  Disconnecting modules and turning the ignition switch to RUN may cause DTCs in these modules. Check for DTCs in each module upon completion of the required repair.  The scan tool cannot directly communicate to the Rear Video/Audio/HVAC or Video Disc Player. Diagnosis is accomplished by checking communications with the Radio. Test Description The numbers below refer to the step numbers on the diagnostic table. 2. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit. 3. DTCs U1300, U1301, or U1305 may be retrieved with a history status. These DTCs are not the cause of the present condition. 6. A state of health DTC with a history status may be present along with a U1000 having a current status. This indicates the malfunction occurred when the ignition was on. 7. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively. 9. poor connection at the DLC terminal would cause this condition but will not set a DTC. 10. An open in the class 2 serial data circuit between the DLC and the star connector will prevent the scan tool from communicating with any module. This condition will not set a DTC. 11. The class 2 serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wiring for a short, make sure there is not a module connected to the wire being tested. This test isolates the PCM class 2 serial data circuit. 13. his test isolates the SDM class 2 serial data circuit. 15. This test isolates the EBCM class 2 serial data circuit. 17. This test isolates the IPC class 2 serial data circuit. 19. This test isolates the PK3 class 2 serial data circuit. 21. This test isolates the DIC class 2 serial data circuit. 23. This test isolates the Radio class 2 serial data circuit. 33. If there are no current DTCs that begin with a "U", the communication malfunction has been repaired. 35. The communication malfunction may have prevented diagnosis of the customer complaint. The modules are numbered to aid in identification of what Class 2 device isn't communication, your is the IPC Instrument panel cluster and the theft deterrent module.

Ok I have tested everything to ground. radio and all and I dont get any shorts. I do not know which pin on the PCM is the class 2 pin do you happen to have a diagram for this year that shows the pin configuration? The only purple wire I am having a "short to ground" (purple is pin #2 on the DTC connector) is pin #30 on the blue connector to the PCM. I was thinking that purple might be ground because the lighting purple is ground. I am also not getting any shorts to power that I can find.

So am I understanding all this correctly? what the Codes are saying is that the most likely problem is coming from the IPC and/or the EBCM? Would disconnecting the class 2 side of the EBCM and then driving around tell me if it is the EBCM causing the issue or would that keep me from driving. Meaning if I remove the connector with the class 2 wiring on the EBCM if this problem happens a small while down the road that would eliminate the EBCM as being the culprit and would mean it is most likely a problem with the IPC? or am I looking at this situation incorrectly?

Pin 2 Diagram of the DLC connector is in the post above trace the pin 2 wire...

Pin 2 goes through the firewall to a 20 pin round connector. I have continuity so there is no break in that line. I also verified that there isnt any chafing of the wire. Then it goes from there to? which is where I stopped because I dont have the patience right now to figure out which pin on the PCM goes to the data 2 line. I work 3rd shift as an industrial mechanic and am an electrical apprentice so im tired lol. I will check this thread when I get up in a few hours.

Check your email, I sent a PDF of the data lines for all modules, this should help you finding the short, there is a data line for each module in the van... Happy hunting!

Ok thanks that helps a ton. The only problem I found is the Driver information Center wire. The print says it is a Yellow wire on pin 15 but there is no pin 15???? Isnt the DIC one of the two plugs that connect to the instrument cluster? I tried the yellow wire that is on the same plug as the grey wire for the IPC but I get no continuity between that and the other end. I also have to remove the seat to get to the airbag control module as I havent tested that yet but I have to leave for work in 1 hour so gotta stop troubleshooting for now. However for what I have tested I have found no shorts to ground (even when moving wires every which way) as well as the correct continuity when testing each end of the wire.

So tomarrow when I get home I will pull the SIR fuse remove the passenger seat and then get to the air bag module and check that wire.

I went to see if I could do a gauge sweep (prob wrong thing to do). I put the key in pushed the button (I call it the oil reset trip meter reset) and turned the key to on. Sweep did not start so I am assuming I am either doing it wrong or that doesnt work with this vehicle. Sorry to get sidetracked I got bored at work and was reading about how to do an IPC sweep.

Some GM's have a plug under the driver's seat, and not for the power seat, it would plug into one coming into the vehicle from outside, if you have one, unplug it and inspect for corrosion and damaged pins, this may cause all your symptoms too...

yeah there is no plug under my seat for that. The only thing I found (finally found that i was going to the wrong wire on the strip for the DIC lol) was there was a BUNCH of dexcool in the compartment with the PCM. I took a rag and cleaned out as much as I could and then used a blow dryer to dry it off. My guess is it got in there when the engine overheated and blew coolant all over the engine compartment (thus why I went and had the manifold gaskets replaced). So far drove it 10 miles and nothing has happened. Then again its not 90+ degrees out and only 72F. If and when it comes back I will take it into the dealership and have them run a tech 2 on it and see if they can at least tell me which part is bad. The cd player in the radio quit working as it wont read a single cd (started not reading them before I started ripping everything apart). So it might be the radio but the radio eye might just be dirty so I dont know. I am leaning more towards the IPC but again without the expensive tools to verify it I am not gonna just change it out lol.

You MUST unplug the wet connector and see if water got insde the plugs, dry them off! You can also remove the plugs at the IPC and inspect both the plugs and the IPC circuit board, many times just unplugging and re plugging fixes problems, GM even sent out a tech bulletin to the dealerships to do just that...

I unplugged both the blue and white connectors and no water got inside them. Did that when I cleaned out the compartment.

Today the van WOULD NOT start. I could hear the fuel pump turn on but I didnt get that "click" sound of it wanting to start. The radio wasnt on so I unplugged it and the van started. All the gauges were completly eratic. I pluged the radio back in and it did not turn on until the instrument cluster stopped doing its dance. Then it would turn back on. I unplugged the IPC and I no longer get the low fuel ding. Though now the radio wont turn on because of how its tied to the IPC. Unplugging and plugging the IPC connectors back in makes it not do any funny stuff for about 1/2 mile then it starts right up again. I am getting 13.6 volts with everything on at the orange and black wires (hot and ground) on the IPC plug so its got plenty of voltage.... Plus I just noticed today that the Odometer is not keeping miles anymore. SSSOOO I am gonna have the IPC sent out to be refurbished as its $100 cheaper than buying a new one and having it programed at the dealership.

Let me know how that turns out!

finally found the problem. The harness coming out of the PCM goes down under the air duct and to the ac accumulator. there was about 100 ish wires in this wire loom (I am estimating but there sure were a ton of wires) and most of them were shorted against the ac accumulator. Holy cow is that alot of work to repair all those wires. I didnt notice it because it was hidden on that side.

That'll do it! Tough finding the little buggers eh? Nice work.

yes very tough especially when there are so many that are so small lol. It seems to have fixed my po420 fault as well but only time will tell on that one. I havent checked to see if the cat test has finished yet or not lol.

You can recheck to see if the o2 sensor is now switching between rich and lean.

My 2004 Silhouette had this problem any time the outside temp went over 26 degrees centigrade. After driving a short while, guages go nuts, traction control, check engine and other lights activate, speedo gets jumpy and the engine stalls.
It will restart almost right away only to repeat the problem shortly.
I traced the problem to the ingnition relay in the fuse/control box, right corner under hood. ( new relay did not help).
High underhood temp, + battery heat ( right under the box) are combining to cause this relay to open temorarily. Driving with the plasic cover removed has cured this hot stall problem. Its never an issue in cooler temps. ( Some models may have less accessories running thru this relay, creating less heat, and so may not have this problem). Venting the cover also helps. I've done this recently.
I would suspect the Venture and Montana will also experience this problem. Hope this helps. Sparkii

He found his problem, could maybe help you as well?
Posted at Mon Aug 30, 2010 2:28 pm
By ofblong, Have Donated
(12) Give Feedback | Votes: 0


finally found the problem. The harness coming out of the PCM goes down under the air duct and to the ac accumulator. there was about 100 ish wires in this wire loom (I am estimating but there sure were a ton of wires) and most of them were shorted against the ac accumulator. Holy cow is that alot of work to repair all those wires. I didnt notice it because it was hidden on that side.

[quote:e9896a8b53="merlin2021"]You can recheck to see if the o2 sensor is now switching between rich and lean.[/quote:e9896a8b53]

sorry I did not see you had replied to this thread. The o2 sensors are switching (both of them are). However it took a week before the cat test was done (Im too lazy to do it the correct way lol). as soon as the cat test was done the po420 fault came right back on. The o2 sensors were reading the same number but are constantly changing from rich to lean. neither sensor stays in the middle (.45). The big reason I am leaning towards the cat being bad is because this van has had 2 eaten through head gaskets. First one at 30k miles (under warranty) second one 36k miles later (just outside of warranty). My problem is I didnt have the $$ to fix it at the time so I drove it till it had 95k miles total on the van (30k miles from when it started leaking). I now had the money to get it fixed however we kept driving it until the engine overheated on us. Thats when we took it right in. So for at least 30k miles the Dexcool was most likely leaking into the cat converter. The other thing is the 02 sensors seem kind of sluggish. as in they change value at most 2 times every second. So it could be all 3 items (up and down stream sensors and the cat). it will prob be another week before I can get the cat changed. Place around the corner from me quoted me $300 to change the cat and well thats only $50 more than I can buy a cat and do it myself so I would rather let them do it for $50 haha. Either way what do you think?

[quote:95b418e54d="Sparkii"]My 2004 Silhouette had this problem any time the outside temp went over 26 degrees centigrade. After driving a short while, guages go nuts, traction control, check engine and other lights activate, speedo gets jumpy and the engine stalls.
It will restart almost right away only to repeat the problem shortly.
I traced the problem to the ingnition relay in the fuse/control box, right corner under hood. ( new relay did not help).
High underhood temp, + battery heat ( right under the box) are combining to cause this relay to open temorarily. Driving with the plasic cover removed has cured this hot stall problem. Its never an issue in cooler temps. ( Some models may have less accessories running thru this relay, creating less heat, and so may not have this problem). Venting the cover also helps. I've done this recently.
I would suspect the Venture and Montana will also experience this problem. Hope this helps. Sparkii[/quote:95b418e54d]

I can see how this "might" cause the issue but I swapped 2 relays (multiple relays are the same on this thing) and the problem didnt follow so I went onto the next thing. as merlin wrote I did find the issue with wiring running across the ac accumulator.

Down stream sensors dont switch, they remain flatlined, upstream sensors are the switching ones, so look for that behavior in the sensors. Also if oil or coolant is on the sensor wiring, or got into the plugs, clean them out...

hmm my downstream sensor is constantly switching just like the upstream sensor.

What that means is your converter material has lost it's efficientcy... time for a new one.

ok finally got the van in (finally had a day off haha). You could hear the cat rattling. either way they did it for $100 less than I could buy the material myself. Either way now the downstream is pretty constant and the upstream still constantly changes from low to high. Thanks for all yer help.

Ok good, your welcome...