Please help. Cannot figure out po742 code
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Please help. Cannot figure out po742 code To start out I'll say I am a generator mechanic at caterpillar but don't have any transmission experience. I bought an 07 tahoe 4wd with the 5.3l for cheap with no 3rd gear and made a poor decision and bought one from fb marketplace from a low mile wrecked 06 tbss awd. Transmission shifts great through all 4 gears until it triggers a p0742 code then shifts hard from the high line pressure. Research told me it was likely tcc solenoid so I was lazy and didn't test resistance or functionality but just replaced and same code comes back. More research led me to the pwm solenoid and replaced it as well with no change so I replaced the converter itself. Fluid was clean before converter but figured replace anyhow and did with filter so now have squeaky clean cherry red fluid. Still same code comes back and hard shifting and overheating trans etc. More research led to the tcm itself so put in the unit from the tbss wirh flash or reprogram just as a test and it same code still. I finally tested tcc and it measured 21 ohms. Back probed tcc circuit from trans case connecter while watching scan tool and driving and 12 volts is only present when tcc is commanded on. From what I've gathered it doesn't seem like an electronic issue but a hydraulic issue instead. Dopped pan and when tcc solenoid is removed I can reach the tcc apply valve in the pump with a finger and I can cycle it into what feels like spring pressure and it returns so don't think it is stuck in the apply position. The regulator valve immediately beside the pwm solenoid is not siezed either and can move freely. Slip speed is low +/- 20rpm when at low speed so the vehicle is stuck in lock up even though it isn't being commanded. Any thoughts or recommendations are much appreciated!!
Last edited by Hazm4t7; May 26, 2025 at 06:36 PM.
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From: BERWICK PA
Issue is the converter regulator valve bore is worn, The fluid bypasses and causes low TCC apply pressure and excessive TCC slip which set the code which sets line at max all the time,
FIXES are several. REPLACE CRV with sonnax requires boring tool. Some replace isolator valve with spring from sonnax that sets a constant pressure around 110 PSI as I remember. Others use the fitzall valve which eliminates PWM all together and puts TCC equal to line which is probably ok in stock configuration , But would not suggest if running WOT lockup as may damage converter backing plate and clutch. Some put the CRV in backwards. I have not done this but many say they do , This would also put converter equal to line. Some block the valve same result, Other like myself add a helper spring which keeps PWM at a slightly higher pressure.Some use this from transgo https://res.cloudinary.com/transgo/w.../4L6-ISO-3.pdf , I have seems to work well. Unfortunately all require removal of valve body unless you get lucky and someone put the clip in from the other side. I do this sometimes as i sometimes have a shorter clip that works well as a just in case thing. But the normal clip upside down you have to be careful of the harness there as the filter pushes it hard against the clip.
In all cases I replace the end cap of the valve train as it is a major leak point in the oil circuit with an o'ringed type
Any of these of these ways will work just depends on how far you want to get into it as long as converter clutch has not yet been damaged.
FIXES are several. REPLACE CRV with sonnax requires boring tool. Some replace isolator valve with spring from sonnax that sets a constant pressure around 110 PSI as I remember. Others use the fitzall valve which eliminates PWM all together and puts TCC equal to line which is probably ok in stock configuration , But would not suggest if running WOT lockup as may damage converter backing plate and clutch. Some put the CRV in backwards. I have not done this but many say they do , This would also put converter equal to line. Some block the valve same result, Other like myself add a helper spring which keeps PWM at a slightly higher pressure.Some use this from transgo https://res.cloudinary.com/transgo/w.../4L6-ISO-3.pdf , I have seems to work well. Unfortunately all require removal of valve body unless you get lucky and someone put the clip in from the other side. I do this sometimes as i sometimes have a shorter clip that works well as a just in case thing. But the normal clip upside down you have to be careful of the harness there as the filter pushes it hard against the clip.
In all cases I replace the end cap of the valve train as it is a major leak point in the oil circuit with an o'ringed type
Any of these of these ways will work just depends on how far you want to get into it as long as converter clutch has not yet been damaged.
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The regulator valve could cause it to stay locked up even though it moved freely? It never caused engine to stall but it was "lugging" so Maybe it wasn't full lockup due to it bypassing. Im unsure and am strictly asking to learn. Well the clip was not upside down but Struggled with it and was able to get the clip out with a lot of persuasion and Chinese water torture. I compared it to the original transmission regulator valve and it is certainly oversized already. It did have an o ring on the end plug but was cut when installed I can only assume because i didn't have a full o ring of pieces so likely to have been still leaking. Would you recommend me to check fitment/tolerance of bore with current valve and if it checks out reseal and send? I don't mind pulling valve body but if it's already been oversized can it be done again or will a new valve body be required? I don't mind any depth of proper correction as long as it will be the longest term fix. Thanks.
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From: BERWICK PA
I am a dummy, p0742 is TCC stuck on, This is a whole different thing. It will be one of the following.
BAD TCC SOLENOID
STUCK OR MISSASSEMBLED TCC VALVE IN VB
BAD TORQUE CONVERTER OR WRONG BOLTS USED.
Not the CRV , However never heard if that causing HIGH line , More likely the feel of a shift with converter applied which will feel quite harsh.
Check TCC solenoid and valve above it first.
Make sure you did not use non OEM TC bolts that are too long.
BAD TCC SOLENOID
STUCK OR MISSASSEMBLED TCC VALVE IN VB
BAD TORQUE CONVERTER OR WRONG BOLTS USED.
Not the CRV , However never heard if that causing HIGH line , More likely the feel of a shift with converter applied which will feel quite harsh.
Check TCC solenoid and valve above it first.
Make sure you did not use non OEM TC bolts that are too long.
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I tested the tcc solenoid via air pressure through the snout with 12v applied and it does stop flow. I have replaced torque converter already and same issue is present. The line pressure is commanded to max only once the code is set. I can reset code and line pressure is normal without hard shifting but is still stuck in lockup. I will look into the bolt/ alignment suggestions. I just used the original flex plate bolts and didn't think anything of it but will look into whether they are contacting the converter but I'm gonna have to say they are not as of now. They gradually tightened up as a usual bolt would rather than going from finger tight to bottomed out and solid quickly but I'll double check. I can feel movement on the apply valve above tcc solenoid but that's all I've done. I have yet to pull the apply valve or check for fluid exhaust restriction on that circuit.
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From: Poplarville, MS
The regulator valve could cause it to stay locked up even though it moved freely? It never caused engine to stall but it was "lugging" so Maybe it wasn't full lockup due to it bypassing. Im unsure and am strictly asking to learn. Well the clip was not upside down but Struggled with it and was able to get the clip out with a lot of persuasion and Chinese water torture. I compared it to the original transmission regulator valve and it is certainly oversized already. It did have an o ring on the end plug but was cut when installed I can only assume because i didn't have a full o ring of pieces so likely to have been still leaking. Would you recommend me to check fitment/tolerance of bore with current valve and if it checks out reseal and send? I don't mind pulling valve body but if it's already been oversized can it be done again or will a new valve body be required? I don't mind any depth of proper correction as long as it will be the longest term fix. Thanks.
I know this will be a pain in the behind, but you could just leave the TCC solenoid out and go on a test drive. If converter doesn't lug the engine, then you know the problem is in the solenoid or its controls.
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From: BERWICK PA
I tested the tcc solenoid via air pressure through the snout with 12v applied and it does stop flow. I have replaced torque converter already and same issue is present. The line pressure is commanded to max only once the code is set. I can reset code and line pressure is normal without hard shifting but is still stuck in lockup. I will look into the bolt/ alignment suggestions. I just used the original flex plate bolts and didn't think anything of it but will look into whether they are contacting the converter but I'm gonna have to say they are not as of now. They gradually tightened up as a usual bolt would rather than going from finger tight to bottomed out and solid quickly but I'll double check. I can feel movement on the apply valve above tcc solenoid but that's all I've done. I have yet to pull the apply valve or check for fluid exhaust restriction on that circuit.
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