Service Slants

Motor,  May 2005  by Rosario, Tom

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Jeep

Incorrect climate control DTCs. If you ever see an early-model 2005 Grand Cherokee with manual temperature control (MTC) troubles, be extremely careful when diagnosing the system! Jeep reports that the DTCs that spit out of the a/c mode switch LED are bogus (the MTC module isn't connected to the CAN bus, so you can't pull codes with a scan tool).

Vehicles affected are those built before 11/28/04 with an MTC module part number of 55111009AF. The MTC system is designed to spit out codes consisting of a tens digit and a ones digit, and it's the ones digit, says Jeep, that will always be screwed up. As an example, a true code 47 (Recirc Door Bound) will display as a Code 46. Oi; you could get a code 2, which doesn't exist, when in reality you're dealing with a code 21. To make matters worse, Jeep says it has no intention of replacing the MTC module for the software snafu! To help you avoid a really bad day, we've designed the chart at right. It consists of the DTC pulled, the correct code and a brief description of the problem area. Tuck it away for future reference.

GM Truck

ABS light on, DTCs set. Some 1999-2004 midsize and full-size GM pickups and SUVs (full list below) may illuminate the ABS light and store DTC C0201 or C0265 in the ABS computer. In addition, code U1041 may set in other modules or you may encounter lost communication between your scanner and the ABS module.

According to GM, all of these problems are probably due to a bad connection at ABS ground GlK), which you'll find on the frame rail just underneath the driver's-side door. Restoring the integrity of the ground should eliminate all the problems. Here's how to go about it:

Start by getting the truck up in the air. Next, locate ground GIlO at the frame rail. Note that several ground wires may be there, but GIlO is the one with the heaviest wire (12-gauge). Disconnect the ground from the rail and use a "whiz wheel" to clean the area in front of and behind the ground connection. Now get a bolt, two star washers and a nut. Install the bolt, ground connection eyelet and star washer on one side of the rail and the other star washer and nut on the other side. Torque the nut to 79 in.-lbs. To complete the fix, spray the bare frame rail with rubberized undercoating (Part No. 12378398 or equivalent), lower the truck, then conduct a road test to ensure that the ABS light stays out.

Trucks that can be affected by the problem are:

1999-2004 Chevy Silverados and GMC Sierras

2000-04 Chevy Tahoes & Suburbans; GMC Yukon, Yukon Denali & Denali XL models

2002-04 Caddy Escalades & Escalade EXTs; Chevy Avalanche, TrailBlazer & TrailBlazer EXT models; GMC Envoys, Envoy XLs & Sierra Denalis; Olds Bravadas

2003-04 Chevy SSRs and Cadillac Escalade ESVs

2004 Buick Rainiers and GMC Envoy XUVs

Ford

Accelerator pedal vibration. Some 2004-05 Taurus/Sable models equipped with the 3.OL four-valve V6 can set up a rather wicked vibration that can be felt through the accelerator pedal while driving. Ford says the problern is most pronounced at speeds between 40 and 42 mph, and is most likely due to improper routing of the accelerator cable at the factory. Repositioning the cable should help eliminate the problem.

Start by disconnecting the air cleaner tube at the air box. Now reroute the accelerator cable so it's positioned over the top of both the brake fluid reservoir and air cleaner tube. There's a small black plastic vacuum reservoir directly above the brake fluid reservoir. Using it as a reference point, secure the cable to its front vacuum hose with a nylon tie, making sure the tie is positioned no more than % in. away from the reservoir body. To complete the fix, reattach the air cleaner tube to the air box, then road-test the car to verify that the vibration has been eliminated.

Acura

Clunking sound from rear. All 2001-03 MDX trucks, as well as 2004 models built between VINs 2HNYD1...4H500001 and 2HNYD1 ...4H514801, are prone to giving off an irritating clunking sound from the rear when the brakes are first applied after changing the direction of the vehicle-say, from Drive to Reverse.

The folks at Acura have traced the noise to the outer rear brake pad(s) binding, then slapping hard against the caliper support and rotor(s) during the directional change. New-design brake pad shims (Part No. 06435-S3V-A01) that allow the pads to glide more smoothly in the support grooves are now available to eliminate the noise complaint. When installing the new shims, Acura recommends lubing them up thoroughly with brake assembly grease M-77, or an equivalent lube. Note that 2004 trucks built after VIN 2HNYDl ...4H514801 already have the new shims installed.

GM Truck

Seeing the light...longer. GM reports that the daytime running lamp bulbs used on many of its 1999-2003 full-size pickups and sport/utes (complete list below) are failing prematurely. The good news is that the General has come up with a new, more durable replacement bulb (Part No. 15199562) for the DRL system. The new bull) is said to be more robust, operates at higher voltage (14 volts) and provides slightly more light than its predecessor. GM recommends replacing the bulbs in pairs. The following trucks can take advantage of the new bulb design: