Too many things at once -- coincidence? I think NOT!!

[km2002]

2001 Jimmy suddenly started throwing a lot of strangeness all at once.

Got a service engine light. Stayed on for about a week, went out without either clearing it with a scanner or fixing what the scanner thought was wrong. About a week later, it came back on. The other day, it went out again. It's still out.

Last Friday I had a working cruise control when I gave the vehicle to a mechanic to replace the heater core. I got it back on Saturday, no cruise control. Checked the fuse; it was fine. This evening, the cruise control started working -- for about six miles, after which the gas pedal kicked back out and again, no cruise control.

My DRLs seem to have become erratic. I replaced the DRL relay once, since they didn't work when I bought the vehicle. And yes, I'm one of those apparently weird ones who actually like having the DRLs. They worked once I replaced the relay; but twice now over the last week it appears the DRLs have failed to come on. At the very least, I haven't seen their reflection in the vehicle in front of me while stopped at a light.

The fog light relay was replaced once. The fog lights actually worked when I first bought the vehicle about six, seven weeks ago; but they failed. Replaced the relay, they've worked ever since -- until tonight, when they appeared to flicker (without dying completely) on the drive home.

When I left home this evening, the ABS warning and brake system warning lights both came on. The brake system warning went out almost immediately; the ABS light stayed with me for about 15 miles. I started the vehicle for the return trip; the ABS light has not returned.

At the same time the ABS light started acting funny, the air bag light started acting strange as well, taking longer than usual to go out after startup, sometimes staying on for a mile or two or more before dropping out.

If these were happening individually, in isolation, I'd suspect the particular system. That they're all happening at the same time, and so erratically, suggests a common systemic fault. I looked up the description of the BCM before posting this; there are symptoms here that don't seem controlled by the BCM.

Does anyone have any idea what may be causing these problems, especially all at once? And if it is indeed the BCM, is there some convenient way to reset it, or am I stuck looking for a new BCM?

Thanks one and all,

km2002

[MT-2500]

Originally Posted by km2002

2001 Jimmy suddenly started throwing a lot of strangeness all at once.

Got a service engine light. Stayed on for about a week, went out without either clearing it with a scanner or fixing what the scanner thought was wrong. About a week later, it came back on. The other day, it went out again. It's still out.

Last Friday I had a working cruise control when I gave the vehicle to a mechanic to replace the heater core. I got it back on Saturday, no cruise control. Checked the fuse; it was fine. This evening, the cruise control started working -- for about six miles, after which the gas pedal kicked back out and again, no cruise control.

My DRLs seem to have become erratic. I replaced the DRL relay once, since they didn't work when I bought the vehicle. And yes, I'm one of those apparently weird ones who actually like having the DRLs. They worked once I replaced the relay; but twice now over the last week it appears the DRLs have failed to come on. At the very least, I haven't seen their reflection in the vehicle in front of me while stopped at a light.

The fog light relay was replaced once. The fog lights actually worked when I first bought the vehicle about six, seven weeks ago; but they failed. Replaced the relay, they've worked ever since -- until tonight, when they appeared to flicker (without dying completely) on the drive home.

When I left home this evening, the ABS warning and brake system warning lights both came on. The brake system warning went out almost immediately; the ABS light stayed with me for about 15 miles. I started the vehicle for the return trip; the ABS light has not returned.

At the same time the ABS light started acting funny, the air bag light started acting strange as well, taking longer than usual to go out after startup, sometimes staying on for a mile or two or more before dropping out.

If these were happening individually, in isolation, I'd suspect the particular system. That they're all happening at the same time, and so erratically, suggests a common systemic fault. I looked up the description of the BCM before posting this; there are symptoms here that don't seem controlled by the BCM.

Does anyone have any idea what may be causing these problems, especially all at once? And if it is indeed the BCM, is there some convenient way to reset it, or am I stuck looking for a new BCM?

Thanks one and all,

km2002

What are your code no.? being set?

[km2002]

No codes on scanner. And to make matters worse since my first post, the ABS light has reappeared and then gone out; the air bag light has stayed too long and then gone out; they tell me the sending unit on the fuel pump's bad, but with everything else electrical going nuts, that's now questionable; and I can shift without engaging the button on the stick, plus I can shift out of park without putting a foot on the brake (but that's been the case since I got the vehicle). I hear things clicking (generally in the area of the steering column) when I push on the shifter button, but I don't need the button to shift.

[4x4 blazerguy]

I'm no computer wiz, but it sounds like a bad ground or grounds. Check body grounds & any others there are, most likely many. Just my thought.

[km2002]

I don't get much from AllData on this subject: An illustration of where the engine ground strap connects to the body near the cowl, and this statement:

Additional ground straps are used to connect the body and the frame to the engine and the transmission. Always connect all ground straps in order to ensure a good ground path to the battery for all electrical components.

Unfortunately, no other information about these "additional ground straps," nor the order in which the ground straps should be connected. Problem grounds make sense; but how many places do I need to check? And does anyone have illustrations?

[MT-2500]

Originally Posted by km2002

I don't get much from AllData on this subject: An illustration of where the engine ground strap connects to the body near the cowl, and this statement:

Additional ground straps are used to connect the body and the frame to the engine and the transmission. Always connect all ground straps in order to ensure a good ground path to the battery for all electrical components.

Unfortunately, no other information about these "additional ground straps," nor the order in which the ground straps should be connected. Problem grounds make sense; but how many places do I need to check? And does anyone have illustrations?

All Data has good info on grounds.
But.
You have to look in right place.
Look under diagrams and also grounds.