Cadillac Catera & Chevy Silverado

This weekly Q&A session answers your questions about cars and trucks. This week explores a 1997 Cadillac Catera that won't start and a 1994 Chevy Silverado that won't shift.

Question: 1997 Cadillac Catera

Hello,

I saw your write up on the net. I have a 1997 Cadillac Catera that won't start. Had it at a shop and they say fuel pump etc is working fine but they can't pick up any codes by using their scanner. They say they tested the cable to the computer and they are working fine. The OBD-II link won't even work for them to access any codes. Do you have any suggestions? I'm thinking it has something to do with the computer.

Thanks,

Gene

Answer:

Not all aftermarket OBD-II scan tools are compatible with the GM diagnostic systems, so it could be a problem with the scan tool and not the vehicles computer. If that is the case then your mechanic will need to get a GM compatible scan tool or you will need to take the vehicle to a Cadillac Dealer.

There was a TSB issued concerning this also.

Bulletin No.: 77-71-58

Date: April, 1997

Subject:

Inability to Establish Scan Tool Communication with the Transmission Control Module (TCM)

Model:

1997 Cadillac Catera with HYDRA-MATIC 4L30E Transmission (ML4) on Vehicles Built from S.O.P. through W06VR52R090366

Some technicians may experience difficulty in establishing scan tool communications with the Transmission Control Module (TCM). The scan tool will display the message No communication with vehicle, check diagnostic link connector, check ignition on/off."

The TCM software only allows communication when directly addressing the TCM. If communication is initially made with the ECM, communication with the TCM is not possible.

Establish scan tool communication with the TCM prior to communicating with the ECM. If communication is established with the ECM initially, cycle the ignition key off for at least 10 seconds, turn the ignition key on and directly address the TCM.

Question: 1994 Chevy Silverado

Hi. Nice site. My 1994 Chevy Silverado 4x4 brake warning light is on and dim, no speedometer or it's erratic at full acceleration. Brake fluid full and A/T fluid okay. The brakes were replaced 2,000 miles ago.

The vehicle was cruising at 35 mph and the light came on and won't shift past 2. I replaced the VSS on the automatic transmission and the light is still on (but dim). 152,000 miles No problems or noises, just seemed to lock-up with no power except full acceleration seems to work from 0 to top speed of second gear. Won't even attempt to shift when let off accelerator?

I don't have an OBD-I scanner and short on funds as it is. Please Help.

Markus

Answer:

You can access the DTC's without a scan tool on this vehicle, see Diagnostic Trouble Codes - 1994 Chevrolet.

All of these conditions can be brought on by the use of an excessively/over-oiled aftermarket, reusable air filter. The oil that is used on these air filter elements may be transferred onto the Mass Air Flow (MAF) sensor causing contamination of the sensor.

It's possible there is a wiring or connector problem. All the connectors, including the PCM connector, should be checked to insure they are clean and tight. The wiring harness should inspected for cut, broken or chaffed wires.

Another possibility is a bad PCM EPROM. If you're getting a code 87 then this becomes more likely. You shouldn't replace this without verification from a technician.

If all else fails then a visit to your Chevy Dealer will be necessary.

That’s all for this week. Feel free to browse the archives for past topics. And, as always, if you are stuck and need an immediate answer you can always call Vince on the phone.

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