Service Slants

Service Slants

Savasta, Bob


Rough idle, MIL illuminated, DTC set. Some 1999-2004 Grand Cherokees, 2000-01 Cherokees and 2000-04 Wranglers, all with the 4.0L inline Six, may exhibit a rough idle for about 30 seconds following a 10to 20-minute soak in hot ambient temperatures (greater than 90°F).

According to Jeep, the problem can be aggravated by high ethanol content in the fuel, is more prominent after stop & go driving and is due to heat from the exhaust manifold migrating to the area around the No. 3 injector. This leads to vapor forming in the injector and causes a misfire in the No. 3 cylinder, which results in DTC P0303 being logged in computer memory. Installing a new insulating sleeve (Part No. 5602H371AA) around the injector should lower its operating temperature sufficiently to prevent a recurrence of the problem.

Begin the repair by cutting the insulating sleeve with a razor blade or XActo knife so you have two equal sleeves about 1 in. long. Install one sleeve around the No. 3 injector, with its slit facing the upward side of the fuel spritzer (see illustration). Install the other sleeve with its slit facing the downward end of the injector. To complete the fix, make sure the sleeves are Hush with the intake manifold surface and that the injector is rotated to the 2 o’clock position (as viewed from the driver’s side of the vehicle) so the wiring doesn’t twist and cause undue strain on the harness connector.

GM Truck

Exhaust pop or snap. A slew of General Motors sport/utes and pickups (complete list below) may produce a loud, irritating popping or snapping sound from underneath the vehicle at idle or immediately after engine shutdown.

The good news hure is that GM service engineers have found the source of the noise: moisture trapped between the layers of the muffler. This moisture tends to turn to steam as it’s super-heated by the exhaust gases. That in turn leads to the expansion of the inner shell of the mufflcr, which deforms and expands against the outer layers and case. Its this contact that results in the popping or snapping noise.

The bad news is that GM doesn’t have a remedy for the problem, at least not yet. Replacing the muffler or other exhaust components won’t result in a fix, so don’t waste your time or your customer’s money. GM is actively working on a solution, and should have one shortly.

The Following vehicles can be affected by the problem:

1999-2004 Chevy Silverados and GMC Sierras

2000-04 Chevy Suburbans & Tahoes and GMC Yukons & Yukon XLs

2002-04 Cadillac Escalades & Escalade EXTs

2003-04 Cadillac Escalade ESVs and Hummer H2s


Fluttering noise on shutdown. Ford wants you to be aware that some: 2000 Focus models (build dates 9/2/99 through 10/1/99) can produce an irritating fluttering sound from the engine bay when the engine is shut off. Powertrain engineers have traced the problem to the natural resonance that sets up in the PCV valve and hose when vacuum to the valve is abruptly terminated at shutdown. A new-design PCV valve (Part No. YS4Z-6A666-AA) and hose (Part No. YS4Z-6758-BA) are now available to address the noise complaint. Figure about .2 hour labor to complete the parts swap.


Battery warning light on, DTC set. Some 2003 Town Cars built before 7/1/02 may illuminate the battery warning lamp on the dash and store DTC P1246 (generator load input failed) in PCM memory. Lincoln engineers say the condition typically occurs when the vehicle is started, then placed in gear and immediately driven, without allowing the engine to return to normal idle. Problem is, under those circumstances, the PCM strategy is set up so it won’t command the alternator to charge, which causes the warning light to go on and the code to set.

A revised PCM strategy is now available to correct the anomaly. You’ll find the software update in WDS release B28.3 or higher. After the reprogramming is complete, make sure you fill out an Authorized Modifications Decal and affix it adjacent to the VECI decal.

GIVI Truck

Headlamp saver. If the low-beam headlight socket corrodes or shorts out on a 2002-03 midsize GM sport/ute (full list below), the General has good news: A replacement socket (Part No. 88987884) is now available to eliminate the problem. Previously, the entire headlamp assembly had to be replaced if the socket went.

To install the new replacement socket, begin by removing the headlamp assembly. Now cut the old, damaged socket from the wiring harness. Using a few wire splice sleeves (Part No. 12089189 or equivalent), splice the new socket into the harness. Cover everything up with electrical tape, then install a new bulb into the socket. To complete the repair, install the replacement socket into the headlamp assembly, then the headlamp assembly back into the vehicle. Total elapsed time for the surgery should be about .3 hour.

Trucks that can benefit from the new low-beam socket are Chevy TrailBlazers and TrailBlazer EXTs, CMC Envoys and Envoy XLs and Olds Bravadas.


Vibration under brakingl Toyota says that 1996-2000 4Runners are prone to giving off a pretty nasty vibration under braking at speeds above 40 mph. Not surprisingly, excess lateral runout in the front rotors is the most likely cause for the complaint.

The Japanese vehicle maker recommends a two-pronged repair approach to get rid of the bad vibes-cutting the rotors, then installing newly formulated front pads (Part No. 04465-35240) that are gentler to the discs’ surfaces. The old shims can be reused if they show no signs of heat discoloration. If they do, order up a new shim kit (Fart No. 04945-35040), as well.

When machining the rotors, Toyota recommends using a quality on-car brake lathe to achieve a runout reading of .0012 in. or less.


Seat bell woes. Owners of 2003 Grand Am models may comment that the seat belt light on the dash stays on or flickers even after the belt is securely buckled. According to Pontiac service engineers, this condition is most likely the result of the seat belt wiring harness chafing on the metal band that wraps around the base of the seat bottom as the seat is moved forward or back.

To confirm the diagnosis, trace the belt harness and look for rub-through in the wiring, paying special attention to the area about 1 in. past where it exits the plastic sleeve on the buckle. If you notice damage, repair the wiring, then protect it by wrapping electrical tape around the repaired area. To avoid a repeat of the problem, place a piece of protective tape on the seat band, then reroute the harness away from the metal edge.


Pressure control solenoid design change. If you’re a transmission rebuilder, you’ll want to know that GM went to a new-design pressure control solenoid in the 2003 model year for its 4T65-E, 4T40-E and 4T45-E transaxles. The new solenoid, which is manufactured by Bosch, is very similar in appearance to the older version that was used in 2000-01 iterations of these trannies, which was manufactured by Delphi.

Caution: The two solenoids are not interchangeable. If you install the new solenoid in an older gearbox or the previous design in a 2003 or newer tranny, says GM, improper or rough shifting will result. For reference, the older-design solenoid goes by Part No. 10478146; the newer solenoid is Part No. 24225825.


Evap leak-detection tips. For your information, Chrysler has streamlined the diagnostics for evaporative system leaks on some of its 1998-2002 vehicles with OBD II systems (full application list below).

Evap leaks will typically turn on the MIL and store one of three codes-P0456 (small leak detected), P0442 (medium leak detected) or P0455 (large leak detected). The leaks are nailed by the PCM using a special Chrysler-developed apparatus known as a leak-detection pump (LDP). On or near the LDP is a vent valve, and its this valve that should be suspected anytime the pump has determined an evap system leak exists. Here’s the diagnostic drill:

Use a component locator manual to find the LDP and vent valve, then get the vehicle up on a lift. Now remove the vacuum hose from the top of the vent valve and attach a hand-held vacuum pump to its port. Apply 20 in./Hg vacuum to the valve and observe the gauge on the pump for 10 seconds.

The vacuum should hold between J 5.5 and 20 in./Hg. If it falls below 15.5 in., the vent valve is leaking. Replace it, making sure all hoses and clamps are securely attached. To complete the fix, drop the vehicle and clear the DTC from PCM memory. If the MIL illuminates and the DTC reappears, says Chrysler, follow the trouble tree to the letter for that specific code.

Vehicles that can benefit from the streamlined diagnostics are 1998-99 Hreeze, Cirrus and Stratus models, as well as 1999 Sebring convertibles with California emissions, all 1998-2001 LH-cars (Concorde, Intrepid, LHS, 300M) and all 2001-02 Town & Country, Caravan and Voyager minivans.


Engine compartment tick. Some 200.1-02 Focus models with the 2.0L 4-cylinder engine (VIN P) may produce a ticking or pulsing sound underneath the hood. Ford says the noise may be accompanied by an illuminated MIL, with DTCs P0401 and/or P0402 stored in PCM memory. According to the carmaker, all these problems could he the result of a defective dash-mounted Delta Pressure Feedback EGR (DPFE) sensor.

If conventional diagnostics lead you to a had sensor, know that an upgraded part is now available. The new sensor is part of a kit (Part No. 3S4Z-9P449-AA), which also contains a new wiring connector and installation instructions.


Loss of power to accessories. Mitsubishi reports that some 1999-2002 Galants and 2000-02 Eclipses (all built prior to 8/10/01) may continually lose power to accessory items like the radio, dome light, sunvisor vanity mirror and keyless entry system. With a wiring schematic in hand and a little detective work, you’ll probably find that IDO fuse No. 4 (1999-2001 models) or No. 18 (2002 models) is blown. Mitsubishi says that the fuse fireworks occur most frequently when the dome light switch is in the OFF position and the keyless entry remote is used to lock or unlock the doors. A short in the dome light switch’s slider mechanism is the most likely cause of the voltage spike that takes out the ruse. Verifying the problem and repairing the mechanism is the quick and lasting fix.

Here’s how to go about it: Begin by removing the entire dome light assembly from the vehicle. Next, put the slider bar in the OFF position and look at the bar’s retaining screw. It’s probably loose, which will cause the slider to rotate just enough to make simultaneous contact with the adjacent switch terminal. To correct that, move the slider bar all the way to the OFF detent and hold it there, then tighten the retaining screw. Now put a drop of Super Glue on the screw and slider. That will keep the screw from loosening and, therefore, the slider from moving. To complete the repair, reinstall the dome light assembly, replace the fuse, then lock and unlock the doors repeatedly with the remote key fob to verify that the fuse can handle the abuse.


No washer spritz. Owners of 2000-03 L-series models built prior to VIN breakpoint 3Y564034 may complain they’re not getting much of a spritz of fluid from one or both windshield washer nozzles. Saturn engineers attribute the problem to the position of the washer supply hose hood hinge clip in relation to the inline hose connector situated between the hood and main body hoses. The mispositioned connector causes the supply hose to be pinched by the hinge assembly when the hood is closed, and that’s what starves the nozzles of the needed solvent. Repositioning the connector forward of the hinge clip should remedy the situation in short order.


Rerrigerant leak-detection tips. Toyota has come up with some great tips for diagnosing a/c refringerant leaks with an electronic leak detector (the carmaker’s preferred method). Begin by doing a quick underhood visual inspection. Look for signs of heavy refrigerant oil accumulation, which suggest possible leakage points. Now clean road dust and dirt from all fittings and joints. Don’t use solvents; they could give you false readings! Electronic leak detectors work best when the system is full, so charge the system and let it run for several minutes to distribute the refrigerant and oil, then shut it down.

Toyota suggests starting your leak-check at the block and piping joints. Refrigerant is heavier than air, so position the detector wand about ¼ in. below the test point. Now move the wand tip slowly across and around each joint in the system.

Next, move on to the evaporator; its drain hose provides an excellent access point to check for leakage, says Toyota. So get the vehicle on a lift and raise it way up in the air to prevent petrochemicals on the shop floor from giving you false readings. When leakchecking the evaporator, pinch off the drain hose, then wait 10 to 15 minutes to allow any refrigerant to accumulate in the evaporator case. Position the wand about ¼ in. below and slightly to the left or right of the drain, then release the hose. Make sure the wand tip doesn’t come into contact with the water coming out of the case.

Front compressor seal leaks are probably the most difficult to nail, so it’s imperative the system is fully charged and operating pressures are on the money. You have gauges; use them! Start the leak-check by positioning the wand across the lower half of the compressor clutch. Move the tip slowly and deliberately back and forth across the bottom of the compressor. Don’t allow the tip to come into contact with normal oil accumulation; that will affect the detectors readings.

Service valves and pressure switches are the last of the possible leakage sources to check in an a/c system. Note that small accumulations of refrigerant under the valve caps or switch connectors are normal. So remove these caps and connectors, then wait about 20 minutes to allow air to circulate and carry away the accumulated refrigerant before leak-testing.

One final point: Don’t use compressed air to flush out the service valve or switch cavities; the petroleum residue from inline oilers or the compressor itself could lead to false readings from your leak detector.

GM Truck

Service 4WD light on and/or inoperative 4WD system. Owners of some 2003 GM full-size pickups and SUVs (complete list below) may comment that the Service 4WD light on the dash is illuminated. They may also complain that the 4WD system isn’t working properly, or at all. According to GM powertrain engineers, the most likely cause for the difficulties is software anomalies in the Transfer Case Control Module (TCCM). Revitalizing the TCCM with some fresh files found in software update TIS version 3.5 or newer should eliminate these four-wheeling problems for keeps.

To find out for sure, hook up your scanner and start checking for codes logged in TCCM memory. If all you get is DTC C0300 and/or C0305, burn in the new software with confidence. If DTC C0374 is found along with one or both of the above-mentioned codes, simply ignore and clear it, then once again commence with the reprogramming. If DTC C0374 or C0550 is found sans the C0300 and/or C0305, proceed with normal diagnostics for those codes; the software update won’t help.

Vehicles that are susceptible to the TCCM glitch and will most likely benefit from the influx of fresh software are Chevy Avalanches, Silverados, Suburbans, Tahoes and TrailBlazers; CMC Envoys, Sierras, Yukons and Yukon XLs; and Olds Bravadas.

Ford Truck

Brake dust complaint. In case you aren’t aware of it, Ford went with a new lining material for the front and rear brake pads of its 2003-04 Expedition and Navigator SUVs. The new friction material is designed to be gentler to the rotor surfaces, which in turn helps keep both lateral runout and thickness variation in check.

But while these new linings do deliver as promised, they have one significant drawback-lots of brake dust spewing from the pads onto the spiffy wheels of the mammoth trucks. And apparently, Ford is hearing lots of consumer complaints about it.

As a result, Ford has come up with yet another friction formulation, this one designed to keep dust in check while minimizing rotor wear. You’ll find the upgraded material in a service kit (Part No. 4L.1Z-2001-BA) that contains both front and roar brake pads. Ford warns that the new pads must be installed as a set, since mixing different formulations will compromise overall braking performance.


Water leak. Somo 2001-02 Millenia models may spring a water leak into the passenger-side footwell area. According to Mazda, the most likely culprit is a deformed rubber seal at the bottom of the evaporator case. The deformation of the rubber causes condensate to drip from the case instead of exiting through the evaporator drain. A new, more pliable evaporator case lower seal (Part No. TC86 61 J31) is now available to stop the leak.

To install the upgraded seal, start by removing the lower cover under the dash on the passenger side. Next, remove the retaining nut, followed by the deformed old seal. You’ll find the seal at the bottom of the evaporator case, covering the air filter access slots. Position the new seal onto the case, then tighten its retaining nut to 10 in.-lbs., making sure the seal is flush with the case and that there isn’t a gap between it and the filter slots. Reposition the seal, if necessary. To complete the repair, reinstall the lower cover under the dashboard, turn on the a/c and check for proper water drainage.


Dashboard noise. Some 2001-03 Mustangs may produce a rattling noise from the dashboard. In addition, the climate control vent vanes may become difficult to adjust. Ford says both problems could be due to the vanes in the vent detaching from the pilot holes in the vent housing.

A new-design replacement vent (Part No. 3R3Z-19893-AB) is now available to address both concerns. To perform the swap, pry out the old vent with a small flat-blade screwdriver, then snap the new vent into the housing with a gentle push. Repeat the procedure for the remaining vents, as needed.

Copyright Hearst Business Publishing Jul 2004

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