Read ST9303-04/03.qxd text version

SPRING 2003

GM ANTI THEFT SYSTEM USAGE

When diagnosing a no start condition these days, it's always a good idea to consider if the vehicle has a theft deterrent system that could be the cause. There's nothing more frustrating than chasing, say, a no crank, or a start and stall, only to find that the system is "only doing its job"! On many older vehicles, you can only check with the owner to see what, if any, after-market " alarm" may have been added. Car companies have increasingly made their own systems available either as options or standard equipment. Since the mid 80's GM has used a variety of anti-theft systems, starting with the high end '86 Corvette, working on down to most of their carlines today. Listed below is a breakdown of factory installed systems you can expect to find in GM cars since the '80s. Also noted are what the system disables along with any relearn the system uses. Note that this article covers what GM calls "VTD" or vehicle theft deterrent systems. These systems prevent the vehicle from being driven. Content Theft Deterrent protects against break in, and will not be covered here. Why is it important for you to know which system (if any) the car uses? Here's an example: you have a '96 Cavalier with a no crank situation. The "THEFT" light is illuminated on the dashboard. After checking the list, it turns out that the Passlock system used on this car does not affect cranking. Now you can chase the starter circuit problem without second-guessing.

Pass Key III­ Uses key and transponder module in column. PCM disables the injectors and the starter enable relay. Module or keys can be "learned" after replacement. Passlock­ Disables the injectors approximately 1-2 seconds after startup. It has no effect on the start circuit. Early car systems were controlled by the IPC (Instrument Panel Control). On later vehicles, system control is determined by: BCM (Body Controller), EVO (Electronically Controlled Orificesteering assist), IPC, and other systems. Replacement of lock cylinder or control module requires a PCM relearn.

Remember: Use this as a general guide! There are too many variations to cover every specific system in this tip. Some car lines use these anti-theft systems on upscale models only, or as an option. Relearn procedures vary from year to year. Make sure you have the proper information before starting diagnostics.

Joe DantuonoTop Gun Technician

VEHICLE USAGE

System

VATS PassKey, PassKey II

Models

Corvette: 1986-88 Buick: Century 97-01, Park Ave 91-96, Lesabre 92-99, Riviera/Reatta 90-01, Regal 94-99, Roadmaster 94-96 Cadillac: Eldorado 89-01, Seville 89-97, Fleetwood 92-96, Deville 90-99, Allante 89-93 Chev: Camaro 89-01, Corvette 89-01, Caprice/Impala 94-96, Lumina, MonteCarlo 95-97 Olds: Cutlass Supreme 94-97, Aurora 95-00, Regency/88 91-99, Toronado 90-93 Pontiac: Firebird 89-01, GrandPrix 94-96, Bonneville 92-99 Buick: Lesabre 2000-on; Park Ave 97-on Cadillac: Seville 98-on, Deville 2000-on Olds: Aurora 01-on Pontiac: Bonneville 2000-on Minivans: Venture, Montana, Silhouette Buick: Chevy: Skylark 96-98 Cavalier 95-on, Impala 2000-on, Malibu 97-on, Monte Carlo 2000-on Pontiac: Sunfire 95-on, GrandAm 96-on Olds: Achieva 96-on, Cutlass 97-on, Intrigue 98-on Trucks: 98-on

PassKeyIII

SYSTEM NAME & PROPERTIES

VATS­ Starter disable. Injector pulse disable during crank. Module programmed to ignition key pellet at factory. No relearn. Pass Key I & II­ Same as VATS except module can "learn" key pellet on first power up after installation. PassKey II disables injector pulse after startup.

PassLock

CATALYST EFFICIENCY AND TROUBLE CODES P0420 AND P0430

AS EASY AS BLACK, WHITE AND GRAY

The chemistry and mathematics behind O2 sensor operation is very involved. For the catalytic converter it's no simpler, and figuring out when one's bad has often been a guess. Many shops have replaced them only to end up with the same problem. With the catalyst efficiency monitor built into OBD2, this is at least one job that has been made a little easier. Relax, this is not an in-depth analysis of the Nernst equation (the mathematical formula for zirconia sensors). This is likely as simple an explanation of the catalyst monitor as you will find anywhere. The post-converter O2 sensor signal has several uses ­ we will look at just one, monitoring converter efficiency. Remember though, that these codes are about how well the cat performs chemical changes to the exhaust gases and not related to vehicle performance. First let's talk about paint. Technician A has a cup that he fills with white paint. He then pours this white paint into a small running mixer that has a drain at the bottom. Technician B has a cup that's the same size only he fills his cup with black paint and pours it into the mixer. Technicians A and B alternate pouring paint: black, white, black, white, and so on. Since the mixer is running, the paint that comes out of the drain is mostly gray with some lighter and darker highlights. If one technician stops pouring in paint then all you get is the other color. If the mixer is shut off you get alternating colors. By looking at the color coming out you can tell what's going on within the mixer. In a similar fashion, the PCM can tell what's going on, or not, within the converter by watching the rear O2 signal. If the PCM forces the system rich then eventually the rear O2 must indicate rich. The same is true for a forced lean condition-the rear O2 must eventually show lean. If the converter is in good shape the rich to lean transition in the rear O2 will be delayed. The only time the rear O2 signal looks just like the front one is when there is nothing going on inside the converter. As an added benefit to the

diagnostician, before setting either efficiency code, the PCM must first verify operation of ALL of the O2 sensors. Later model systems will check the converter at idle, older systems perform the tests at highway cruise speeds. The heater circuit of each O2 sensor must pass a functional test. Each O2 must change from rich to lean, and from lean to rich, within a certain time frame to ensure that the sensor is not lazy or biased. These two codes will usually appear by themselves, after about 75,000 miles, with no complaints other than the MIL(Check Engine light) being on. These codes have appeared when improperly manufactured converters were installed. Remember that catalytic converters can become damaged, or poisoned, by many things that will drastically shorten their useful lifetime. Phosphorus from burning oil, lead, silica, sulfur, and poor engine performance such as misfiring will affect converter as well as O2 function. Silicone, another O2 and cat killer, can be found in many products that make things squeak-free and/or shiny. These products should not be used when the engine is running.

Remove the coil from its mounting. This is no easy task on most applications. To make it easier you may consider removing the cables from the power junction block, unbolting it and securing it out of the way to gain access. Clean out all coolant residue from the connector, and install a new coil. Also verify proper coil trigger from the PCM. We have seen situations where the electrical short created by the coolant leak has damaged the PCM driver.

Richard MooersTop Gun Technician

GM VEHICLES­ LATE 1980'S TO MID 1990'S­ LACK OF POWER

This problem can affect many late 80's to mid 90's GM vehicles (cars & trucks) that use a single wire knock sensor that is hard wired to the PCM. Our example vehicle is a 91 Chevy pickup with a 5.7-liter engine and a 4L80-E transmission. Any sensor values or code setting parameters given are for this vehicle only. Parameters may vary with year and model, etc, but the basic principle will be the same. The vehicle may come into your shop with a customer complaint of moderate to severe lack of power. Typical checks of fuel pressure, back pressure, sensor values, ignition timing, compression, etc. do not provide any clues to the source of problem. At this point you may need to look closer at the knock sensor circuit. Typically, these systems use a 3900-ohm knock sensor that is hard wired to the PCM. The PCM provides a 5-volt reference, which is pulled down to approximately 2.5 volts by the sensor. The computer senses knock by interpreting ac voltage generated by the knock sensor. The AC voltage `rides' on the 2.5v DC `carrier' signal. The computer usually makes two functional checks of the knock sensor system. If it fails either of these tests, the computer sets a code 43. The first test is performed by checking that the carrier signal voltage remains below 4.16volts and above 0.64v. The second is a dynamic test. When driving at a light load-steady throttle, the computer will deliberately advance the ignition timing and listen for the beginning of detonation. If it

Jeff AuerbachDiagnostic Specialist

FORD TRUCKS WITH 5.4L ENGINES­ MISFIRE

If you encounter a late model Ford Truck with a misfire usually on cylinder #3 and/or cylinder #4 there are a few common pattern failures worth investigating. The ignition system used on this engine is COP (coil on plug). Each cylinder has it's own ignition coil mounted into the valve cover, then onto the spark plug. The ignition coil is triggered directly by electronic drivers in the PCM (Powertrain Control Module). The root of misfire problems like this can usually be traced to a loose heater hose clamp at the pipe connection. When this clamp becomes loose, it usually allows engine coolant to leak onto the individual coil and causes it to short out.

doesn't detect detonation, it will set the code. Not all systems perform the second test. Now back to our problem vehicle. If you look at your scan tool you may notice that it starts indicating knock even under the slightest acceleration/load condition. This will be your clue to the fix. At this point check the voltage on the blue wire at the knock sensor while it is plugged in the KeyOn, Engine-Off position. You will probably find that it is somewhere around 4 volts, but just under the 4.16v that would have triggered a code 43. If so, suspect that the incorrect knock sensor has been installed in the vehicle. Most likely, it is a 100K ohm sensor that is normally used on older trucks & carbureted vehicles that use an external ESC module. If the voltage had been over 4.16 a code 43 would have set shortly after start up and you would have an immediate clue as to what area to start checking out. However since the static voltage on the circuit was just less than about 4.16volts, the PCM did not set a code. However, because of the incorrect carrier voltage, the dynamics of the knock sensor circuit will be out of design parameters and normal engine noises may be interpreted by the PCM as knock or ping. Since the PCM is seeing almost constant knock, it retards the ignition timing way too much, resulting in the customer's complaint. Since a code is not set, you can end up exhausting all of your normal diagnostic routines without coming up with an answer. In general, on both trucks and cars (although there are a few odd ball exceptions) GM uses three different styles of knock sensor circuits. The first one is the 100K ohm sensor (mistakenly installed on our problem vehicle) that is used on vehicles equipped with an external ESC module. The sensor is hard wired to the ESC module and not to the ECM/PCM. This system does not use reference voltage on the sensor circuit. The second type uses a 3900 ohm sensor (the one that should have been used on our problem vehicle) that is used on vehicles equipped with a single knock sensor wired directly to the PCM. The PCM provides a 5v reference, which is pulled down to 2.5v by the sensor. (Some VIN "1" supercharged vehicles use two 3900 ohm sensors in parallel that pull the carrier voltage down to about 1.3v) The third type uses an 8200-ohm sensor and is used on 4.3L trucks that use two knock sensors wired in parallel. Again the PCM

provides a 5v reference which is pulled down to 2.5v by the TWO sensors. When replacing a knock sensor it is a good idea to temporarily install it in the circuit & ground it to the engine block, then check the KOEO voltage on the circuit. Normally it should be about 2.5 volts. Although (as noted above) there are a few cars that use dual knock sensors where the 5v reference will be pulled down to about 1.3 volts. However if you see the signal voltage over 4v with the sensor plugged in and grounded, DO NOT install the sensor. You most likely have the wrong one. One final item to keep in mind when installing knock sensors is that they must be torqued to 14 ft/lbs. Overtorquing will not only impair the sensor's performance, it could damage it.

found the source of your problem. When valve timing is set correctly, your distributor should be right in the center of its slot. Now is the time to check that timing belt alignment, as well as the crank and cam sprockets for damage. Also inspect the dowel pins and tensioner arms. Keep in mind that an incorrect or a severely stretched timing belt may also create this problem. One last item to check is for a distributor shaft that has spun. This is where the roll pin that holds the gear to the shaft has become damaged, or is missing. This causes the distributor to be out of time with respect to the engine.

John RogersDiagnostic Specialist

Peter Mc ArdleDiagnostic Specialist

OVERHEAD CAM ENGINES WITH A DISTRIBUTOR­ DRIVEABILITY PROBLEMS &/OR LACK OF POWER

You have probably seen this scenario more than once: a vehicle is dropped off to your shop, symptoms are a lack of power or some other driveability issue. The customer has been to more than one shop in an effort to get the vehicle repaired. Probably some "hi-tech" items have been replaced with no positive results. Symptoms may include a bog on snap-throttle, and/or an idle quality problem. Initial inspection indicates fuel pressure is within specifications, and adding fuel doesn't help, maybe even making the condition worse. Spark seems to be strong. OK, lets check that base timing, sure enough base timing needs to be adjusted. We adjust timing and the vehicle is better but not perfect. Hmm. Take a look at the slotted area on the distributor housing. Is that distributor assembly turned all the way to one side and hitting against the stop? If it is, you have

HEATED SEAT DIAGNOSTICS­ GM TRUCKS

At some point, you may be doing diagnostics or confirming a repair on a late model GM truck heated seat system. You seem to be unable to get the passenger seat to heat up. Power, ground, and switch inputs are there, but you have no heat. If you find yourself in this situation, try one more item: buckle the passenger seat belt! Some earlier diagrams and flow charts neglect to mention the use of a seat belt switch that will disable the passenger heated seat relay. The logic behind this is that if anyone were to be sitting in that seat, they would be buckled in. The heater is disabled if the seat is unoccupied to lower unnecessary electrical load.

Joe DantuonoTop Gun Technician

WIRING DIAGRAM COLOR IDENTIFICATION

Interpreting complicated wiring diagrams can sometimes test the patience of the best of us. Sometimes, wire color identification will differ from one manufacturer to another. We included a chart listed by manufacturer in an attempt to correctly identify the correct wire colors the next time you're working on that difficult problem. Richard MooersTop Gun Technician

WIRE COLOR ABBREVIATIONS

BLACK

MAKE

ALFA ROMEO ACURA AUDI (LATE) AUDI (EARLY) BMW CHRYSLER FORD (EARLY) FORD (LATE) GM HYUNDI ISUZU JAGUAR KIA LAND ROVER LEXUS MAZDA MERCEDES MITSBISHI NISSAN PORSCHE SAAB SUBARU SUZUKI TOYOTA VOLKSWAGEN VOLVO BLK BLK SW BK SW BK BK BK BLK B B B B B B B BK B B BK or SW BK B B B SW SB

LIGHT BLUE LT BLU LT BLU

BLUE BLU BLU BL BL BL BL BL BU BLU L L U L U L L BU L L BL BU L BL L BL BL

DARK BLUE

BROWN TAN BRN BRN BR BR BR BR BR BN BRN BR BR N BR N BR BR / T BR BR BR BR BR BR BR BR BR BN

DARK BROWN

LIGHT GREEN LT GRN LT.G LG LG LG LT GRN L LG LG LG LG LG LG

GREEN GRN GRN GN G GN G GR GN GRN G G G G G G G GN G G GN GN G G G GN GN

DARK GREEN

LB LB LB LT BLU LI LB LU LB LU LB SB SB LB LBL SB

DB DB DB DK BLU

DG DG DG DK GRN

DL

DG DG

CH

LG LG LG LG LG

WIRE COLOR ABBREVIATIONS MAKE

ALFA ROMEO ACURA AUDI (LATE) AUDI (EARLY) BMW CHRYSLER FORD (EARLY) FORD (LATE) GM HYUNDI ISUZU JAGUAR KIA LAND ROVER LEXUS MAZDA MERCEDES MITSBISHI NISSAN PORSCHE SAAB SUBARU SUZUKI TOYOTA VOLKSWAGEN VOLVO GREY SLATE GRY GRY GR GY GR GY GY GY GRA GR GR S GY S GR GY GY GR GY GR GY GR GR GR GR GR LILAC NATURAL ORANGE ORN ORN LI OR OR OR O OG ORN O O O O O O O O OR OR OG OR O O LI OR P VO RS PK PK PK PNK P P K P K P P PK P P PK PK P P P V VI VT P VT PPL V P V P V PU / V VI V PU VI or LI VT V V PINK PNK PNK PURPLE VIOLET PUR RED RED RED RO R RT RD R RD RED R R R R R R R RD R R RE or RT RD R R R RO R SILVER COPPER WHITE WHT WHT WS W WS WT W WH WHT W W W W W W W WT W W WT or WS WH W W W WS W YELLOW YEL YEL QC Y GE YL Y YE YEL Y Y Y Y Y Y Y YL Y Y YE or GE YE Y Y Y GE Y

N NA

SR

N

CU

ST9303-04/03

Information

ST9303-04/03.qxd

4 pages

Find more like this

Report File (DMCA)

Our content is added by our users. We aim to remove reported files within 1 working day. Please use this link to notify us:

Report this file as copyright or inappropriate

387836


You might also be interested in

BETA
LittleBook98R
ST9303-04/03.qxd