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Automotive Industry

Service Slants

Motor, Nov 2007 by Rosario, Tom

GM/GM Truck

Door latch freeze-up. Owners of 2003-07 GM cars and light trucks, including 2003-06 HUMMER H2s and 2006 HUMMER H3s, may complain that one or more of their door latches freeze in extremely cold temperatures. According to GM, the freezeup issue is a result of the design of the door latch detent lever coupled with water entering the latch assembly from a car wash or wet road surfaces. Spraying all the latch detent levers in the vehicle with GM Super Lube (Part No. 123446241) should help solve the freeze-up problem permanently.

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Before spraying the lube, make sure the strikers properly engage the latches and that there are no obstructions preventing the doors from fully closing. If everything looks good, use a hair dryer to thaw the latch, then apply compressed air to the latch assembly for several seconds to remove all remaining moisture. Referring to the illustration at right, direct the spray tube of the Super Lube into the latch assembly as shown, then coat the slashed area of the detent lever liberally with the lubricant. Make sure you coat both sides of the lever. To complete the repair, operate the door latch several times to distribute the lube, then move on to the remaining latches in the vehicle.

Ford Truck

No tach signal, warning lamps on, no crank after shutdown. Some 2007 Ford Expeditions and Lincoln Navigators may lose their tach signal, with one or several warning lamps illuminated on the instrument panel. In addition, the truck may not crank on the next attempted start-up after shutdown, with the MIL illuminated and DTC P1260 (Theft Detected, Vehicle Immobilized) logged in computer memory.

According to Ford, all these problems could be the result of a bad or intermittent connector leading to one or more of the various CAN modules in the truck-instrument cluster (IC), restraint control (RCM), antilock brake (ABS), transmission control (TCM) or PCM. Determining which connector is at fault is a matter of connecting your scan tool or other test equipment to see which modules you can and can't communicate with.

Here are a few of the various scenarios: If you can communicate with the IC module but fail in your attempt with the RCM, ABS, TCM or PCM, check for loose or damaged pins 62 and 63 at both sides of connector C238. Similarly, if you can make contact with the IC and RCM but fail with the ABS, TCM and PCM, check pins 12 and 13 at both sides of connector C212. If your test gear makes contact with the IC, RCM and ABS but draws a blank with the TCM and PCM, check pins 20 and 21 at both sides of connector C146. If you can communicate with all of the modules except for the PCM, check pins 13 and 14 and 20 and 21 at both sides of connector C246.

Continuing, if you can't make contact with any of the modules, grab a few wiring schematics and start troubleshooting the various circuits. Finally, if you can communicate with all of the modules and the symptoms persist, you're likely dealing with an intermittent connection at one or more of the connectors mentioned above. Your only recourse is to check each of the connectors individually to pinpoint which pins may be loose or damaged.

Once the affected pins have been identified and repaired, clear the P1260 code, start the engine and check for any other DTCs that may have stored in the modules.

Chrysler

Interior lighting troubles, fluctuating brake lights. The owner of a 2004 Chrysler minivan (Town & Country, Garavan or Voyager) may comment that the interior lights can't be adjusted with the dimmer switch when the headlamp switch is in the ON or AUTO position. If the vehicle was built between 7/1/03 and 8/11/03, the owner may also complain that the intensity of the brake lights fluctuates when the brake pedal is applied. According to Chrysler, both problems are most probably due to software glitches in the body control module (BCM).

To make a definitive diagnosis, hook up your scanner and look up the part number of the BCM software in the vehicle. If it's 04836966AF or lower, you'll need to flash the BCM with updated files you'll find on TechCONNECT If the software part number is higher than 04836966AF, the new files are already loaded into the BCM. Continue with conventional troubleshooting until the problem is resolved.

MIL on, erratic transmission shifts, poor acceleration. According to GM, all of its 2007 and earlier model cars and light trucks (including HUMMER H2s and H3s) can suffer from seemingly unrelated driveability issues. Among the complaints you might hear are that the vehicle accelerates poorly from a stop, or that the engine bogs or has a limited rpm range. In addition, the transmission may shift erratically or slip. Finally, both the engine and transmission concerns may be accompanied by an illuminated MIL.

Start your troubleshooting as you normally would-by connecting your scanner to the DLC. If the only code you pull is related to the mass airflow sensor, GM recommends heading for the air cleaner assembly and taking a quick look at the type of air filter used. Apparently, quite a few owners are replacing their conventional paper filters with a reusable type with a sponge element. Problem is, they overoil the element. The excess oil then makes its way down the air induction duct and onto the hot wire of the MAF sensor, skewing its signal. And that's what causes all the driveability issues.

Automotive Industry

Service Slants

Motor, Nov 2007 by Rosario, Tom

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