2000 Blazer 4L60E, P0740 code.

[c502cid]

2000 Chevy Blazer 4x4. 4L60E with 216k miles on it, I've put on the last 100k. Just an around town and airport beater. Since I got it regular pan drops and filter changes every 20k miles, using whatever Dex3 was around. Just recently set a CEL with a P0740. Cleared it and came back immediately. Code reads as a TCC Control Malfunction. I'd swear the torque converter is locking but maybe not, gas mileage dropped from 16 to 14 or so. Otherwise the trans shifts fine up and down. Fluid is full and doesn't smell burnt. Common problem on the S10/Blazer forums it seems.

Other strange thing it does, sometimes, when you start it in park it feels like it wants to go forward, but obviously doesn't. I push on the brake pedal now when I start it, just in case.

Any easy low hanging fruit to check or change before I put some electrical tape of the CEL? Change the TCC solenoid maybe? Hoping Clinebarger will jump in with some advice, but everyone's internet guesses welcome too! Thanks all!

 

[clinebarger]

What I do is.....
*Backprode the PCM at pin 10 of the C1 connector (Tan with a Black stripe).
*Couple different approaches here.....
1. With a test light connected to B+, Probe the backprobe & command the TCC Enable Solenoid ON with a scan tool. It should light up.
2. With a multimeter hooked to Ground, Probe pin 10 with the Key On, It should be near battery voltage & no voltage with the key off.
3. With a 5amp fused jumper wire hooked to ground, Key on, Toggle the jumper to pin 10, You should hear the solenoid click.

*If #1 passes & #2 & #3 fail, Unplug the Trans Connector & probe pin T (Tan with a Black stripe) again with a test light hooked to B+.....Command the TCC Enable Solenoid ON, Does the test light illuminate?
*I have a 4L60E/4L80E test-breakout harness for Ohming & Click/Amperage testing solenoids, Depending how hard the Trans Connector is to get to....I sometimes Click Test the offending solenoid first.

TCC Enable Solenoid failure isn't exactly common, I run across more wiring issues than anything with this DTC. Wiring issues can be Internal &/or External. The TCC Enable Solenoid is part of the Internal Solenoid Harness.....Rostra makes quality replacements at a fair price.

Circuit diagram & a pic of my breakout harness....

 

[c502cid]

What I do is.....
*Backprode the PCM at pin 10 of the C1 connector (Tan with a Black stripe).
*Couple different approaches here.....
1. With a test light connected to B+, Probe the backprobe & command the TCC Enable Solenoid ON with a scan tool. It should light up.
2. With a multimeter hooked to Ground, Probe pin 10 with the Key On, It should be near battery voltage & no voltage with the key off.
3. With a 5amp fused jumper wire hooked to ground, Key on, Toggle the jumper to pin 10, You should hear the solenoid click.

*If #1 passes & #2 & #3 fail, Unplug the Trans Connector & probe pin T (Tan with a Black stripe) again with a test light hooked to B+.....Command the TCC Enable Solenoid ON, Does the test light illuminate?
*I have a 4L60E/4L80E test-breakout harness for Ohming & Click/Amperage testing solenoids, Depending how hard the Trans Connector is to get to....I sometimes Click Test the offending solenoid first.

TCC Enable Solenoid failure isn't exactly common, I run across more wiring issues than anything with this DTC. Wiring issues can be Internal &/or External. The TCC Enable Solenoid is part of the Internal Solenoid Harness.....Rostra makes quality replacements at a fair price.

Circuit diagram & a pic of my breakout harness....

Thank you! I appreciate the insight to this.