Puzzling overdrive problem... possible pcm issue

FWC_Bronco

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Hi All,

Fist off, it's great to see this site is still "bucking". I joined close to 12 years ago as a teenager when I bought my 95 (unfortunately I lost my original email).

It's nice to see familiar users like Miesk still providing a wealth of knowledge.

That being said, here's what has me stumped:

I'm dealing with a loss of overdrive among other things.

After I had my E4OD rebuilt it starting leaving OD engaged at idle and would subsequently kill the engine (after warm-up). I took it back to the shop and they "fixed" it by clipping the purple/yellow wire by the computer. I ended up wanting to fix things myself after losing confidence in the shop.

I found the solenoid connector harness had rotted so I soldered in a new one and installed a new solenoid pack when I changed my AT filter. I also replaced the MLPS and soldered in a new harness for it (followed the proper alignment guidelines). Overdrive would still not engage so I ran a switch inside the cab and verified the TC locks up. I am temporarily using the switch to prevent overheating. There is continuity from the pcm pin to the connector pin on the tranny.

Here are my other symptoms:
overdrive light is not blinking (button is still functional)
rough putting into gear
rough shifting or shifting from 1-2 entirely too quickly causing acceleration problems.
WILL NOT SHIFT FROM 1-2 MANUALLY
no cruise control
abs light
speedometer bounces at 70+ (overdrive worked before so I wouldn't think this is an issue).


If I reset the computer it will shift smoother but will not engage OD. Also, on cold-starts it will rev extremely high and then almost die, or I have to feather the pedal to get it to start. After the engine is warm this is not an issue. I also replaced the TPS at some point and verified the voltage but I will recheck this after work.

Best,
AL
 
Last edited:

miesk5

96 Bronco 5.0
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Yo Al,
Welcome!
As you cited, I have no idea of what the so-called shop did in the rebuild so I'll address the Speed Control recall and the DTCs for now.
Was speed control, if equipped recall work completed by dealership? Call local dealer or register and view status @ Welcome to Ford Owner | Official Ford Owner Site; or @ Recalls Look-up by VIN (Vehicle Identification Number) ... have VIN ready.
"Summary: ON CERTAIN PICKUP TRUCKS, PASSENGER VEHICLES, SPORT UTILITY VEHICLES, AND MOTOR HOMES CHASSIS, THE SPEED CONTROL DEACTIVATION SWITCH MAY, UNDER CERTAIN CONDITIONS, LEAK INTERNALLY AND THEN OVERHEAT, SMOKE, OR BURN. THIS COULD RESULT IN AN UNDERHOOD FIRE."
See this guide by jowens1126 to confirm recall status @ 93 & 94-96 Cruise Control Recalls Repair
Note that the 93 recall is different than 94-96.
《•••°°°》
DTC Torque Converter Clutch (TCC) Solenoid:
Torque converter clutch solenoid provides torque converter clutch control by shifting the converter clutch control valve to apply or release the torque converter clutch.
Symptoms: Failed on — engine stalls in drive at idle low speeds with brake applied or manual 2. Failed off — converter clutch never engages. May flash transmission control indicator lamp.
Diagnostic Trouble Codes: 629,* P0741,** P0743,** P1743, P1742, P1744. (*Output circuit check, generated only by electrical condition. **May also be generated by other non-electronic related transmission hardware condition.)
DTCs 621, 622, 626, 629, 641 and 652 indicate solenoid did not change state when requested by the Powertrain Control Module (PCM).
DTC 566 or 629 indicates the CCO or SS3/4-4/3 did not change state when requested by the PCM.
Possible causes:
Damaged solenoid/assembly.
Open or shorted harness (internal/external).
Damaged PCM.
Note: Do not use an obsolete Ford STAR Tester for this step. Use a VOM or DVOM.
Disconnect electrical connector on the speed control servo, if equipped.
VOM/DVOM on 20 volt scale.
Connect negative test lead to STO circuit at Data Link Connector (DLC) and meter positive test lead to B+.
Jumper STI circuit to SIG RTN at the DLC.
miesk5 Note, here is the DLC PIN DIAGRAM;


Perform Key On Engine Off Self-Test until Continuous Memory DTC have been displayed.
VOM/DVOM will indicate less than 1.0 volt when test is complete.
Depress and release throttle.
Does voltage increase?
Yes REMAIN in Output State DTM. GO to TC2.
No DEPRESS throttle to WOT and RELEASE. If STO voltage does not go high, PERFORM Pinpoint Test Step QC1. Leave equipment hooked up.

TC2 CHECK SOLENOID ELECTRICAL OPERATION
Key on, engine off.
Disconnect transmission connector.
Using a mirror, inspect both ends of the connector for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Refer to the schematic and table of this Pinpoint Test.
Connect VOM/DVOM positive test lead to VPWR circuit and negative test lead to solenoid circuit of the transmission vehicle harness connector.
miesk5 Note, here is the 95 E4OD Solenoid Connector pin diagram;

VOM/DVOM on 20 volt scale.
While observing DVOM, depress and release throttle several times to cycle solenoid output ON and OFF.
Does the suspect solenoid output voltage change at least 0.5 volt?
Yes RECONNECT connector. REFER to the Transmission Group in the Service Manual.
No REMOVE jumper wire. GO to TC3.

TC3 CHECK CONTINUITY OF SOLENOID SIGNAL AND VPWR HARNESS CIRCUITS
Key off.
Solenoid transmission connector disconnected.
Disconnect Powertrain Control Module (PCM). Inspect for damaged or pushed out pins, corrosion, loose wires, etc. Service as necessary.
Install breakout box, leave PCM disconnected.
But this set of tests includes use of Ford's old Break-Out Box; so, as I mentioned in another thread here; In place of the break-out box, go to the EEC connector pin instead; Substitute EEC connector pin Number for breakout box number



EEC IV 60 Pin Connector Pin Diagram by Ryan M

EEC IV Connector Pin LEGEND Bronco & Ford Truck & Van: 4.9, 460, 5.0, 5.8;
Source: by Ryan M at Ford Fuel Injection

Refer to schematic and table in this Pinpoint Test.
Measure resistance between suspect PCM signal output pin at the breakout box and signal output pin at transmission vehicle harness connector.
Measure resistance between Test Pin 37/57 at the breakout box and VPWR pin at transmission vehicle harness connector.
Is each resistance less than 5.0 ohms?
Yes GO to TC4.
No SERVICE open circuit(s). REMOVE breakout box. RECONNECT all components. RERUN Quick Test

TC4 CHECK SOLENOID HARNESS FOR SHORTS TO POWER OR GROUND
Key off.
Breakout box installed, PCM disconnected.
Transmission connector disconnected.
Refer to schematic and table in this Pinpoint Test.
Measure resistance between PCM signal output pin and Test Pin 37/57 at the breakout box.
Measure resistance between PCM signal output pin and Test Pins 40/60 and 46 at the breakout box and chassis ground.
Is each resistance greater than 10,000 ohms?
Yes REFER to Service Manual, Transmission Diagnosis for internal harness and solenoids. IF OK, REPLACE PCM. REMOVE breakout box. RECONNECT all components. RERUN Quick Test.
NonSERVICE short circuits. REMOVE breakout box. RECONNECT all components. RERUN Quick Test.

I can't find QC1. Will look for it tomorrow.
⊙⊙⊙
 

miesk5

96 Bronco 5.0
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Yo,
Part 2.
The "Site upgrade" limits number of characters in a thread.

DTC 558: indicates a failure in the EGR Vacuum Regulator (EVR) solenoid circuit/Damaged EVR solenoid; Open harness, Shorted harness, Damaged Powertrain Control Module (PCM). ;
Install breakout box, leave PCM disconnected. Measure resistance between Test Pin 33 at the breakout box and EVR circuit at the EVR solenoid vehicle harness connector. Is resistance less than 5.0 ohms?
No - SERVICE open circuit. REMOVE breakout box. RECONNECT all components.RERUN Quick Test.
Yes - GO to DN13.
DN13 CHECK EVR CIRCUIT FOR SHORT TO POWER OR GROUND. Key off. EVR solenoid disconnected.
Breakout box installed, PCM disconnected. Measure resistance between Test Pin 33 and Test Pins 37 and 57 at the breakout box. Measure resistance between Test Pin 33 and Test Pin 40, 46 and 60 at the breakout box.
Is each resistance greater than 10,000 ohms?
No - SERVICE short circuit. REMOVE breakout box. RECONNECT all components. RERUN Quick Test. If DTC is repeated, REPLACE EVR solenoid.
Yes -REPLACE PCM. REMOVE breakout box. RECONNECT EVR solenoid. RERUN Quick Test.."
Source: by Ford via miesk5 at FSB
as I mentioned in another thread here; In place of the breakout box, go to the EEC pin instead; for instance - Measure resistance between Test Pin 33 and Test Pin 40, 46 and 60 at the breakout box. Substiture EEC for "breakout box"
•●•

DTC 332 & Possible Causes; "...EGR valve sticking closed EGR valve diaphragm leaks EVR solenoid sticking closed Loss of vacuum to or from EVR Open in EVR VPWR or driver circuits ..."
Source: by latechsho at Super High Output

Testing; "...There shouldn't be any vacuum at the EGR valve at idle or any time your ass is under the hood fiddling with it, to put it plainly, except for perhaps a very light residual vacuum from the EVR. Check ALL of your vacuum lines FIRST, and the vacuum reservoir for leaks..."
Source: by SigEpBlue

EVR TESTING; "....check the filter on the solenoid. If this is clogged it will inhibit the venting of the solenoid; "...EVR Solenoids should be 20 to 70 ohms (100 to 135 ohms for 7.5L engines). A functional test can be performed on most applications by using a Scan Tool. Enter the Output State check and cycle the accelerator pedal. This will turn all the solenoids on and off. Using a DVOM monitor the voltage at the EGR solenoid(s). They should toggle from a high voltage to a low voltage. Typically this is stated in the manuals and scan tools as above 10.5 volts to below 2 volts. If the voltage does not toggle make sure that you have system voltage on the power side of the connector. If system voltage is present and the voltage does not cycle to the low side check the connector and wiring to the PCM. If the wiring and connector are okay the problem may be in the pin at the PCM or the driver in the computer itself..." by Tomco.
======
EVP Testing & Replacement @
EGR Valve Position (EVP) Sensor Testing & Replacement by Seattle FSB

■⊙■
DTC 334
334 EGR (EVP) closed valve voltage higher than expected

Make sure your EGR valve is closing all the way. Carbon can build up preventing it from closing.

Failed sensor, & as rla2005 wrote; carbon between EGR pintle valve and seat holding the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the flange side of the EGR by mouth. the egr is not closing properly which can cause detonation. remove the egr and clean off any carbon built up on it with carb cleaner and a brush if necessary.

The EGR Valve Position (EVP) Sensor used exclusively by Ford, can be the cause of driveability problems without ever setting any trouble codes. The relationship between the EVP sensor and the EGR valve is important to understand. Either one being out of spec can cause similar symptoms. Understanding this relationship will help you to diagnose uncoded driveability problems like stumbles, hesitations, rough idles and stalling.
EGR Valve Position (EVP) Sensor Testing & Replacement @ EGR Valve Position (EVP) Sensor Testing & Replacement
by Seattle FSB
¤¤¤
by another Al
 

FWC_Bronco

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Measure resistance between PCM signal output pin and Test Pin 37/57 at the breakout box.
Measure resistance between PCM signal output pin and Test Pins 40/60 and 46 at the breakout box and chassis ground.
Thanks, Miesk!

I need some clarification on the above test.

Do I test these pins individually against pin 60 (breakout box)? For instance, would I put one lead on pin 53 (TCC lockup output) and the other lead on pin 60? Sequentially, would I then measure resistance between pin 37 and 60? How is the chassis ground incorporated into this?

I also posted links of my computer for review.

Thanks again!
 
Last edited:

miesk5

96 Bronco 5.0
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Yo,
No, go to the EEC connector pin instead; test between EEC pin number 37 and VPWR pin at transmission vehicle harness connector.

Do same for EEC pin number 57 and VPWR pin at transmission vehicle harness connector.





EEC IV 60 Pin Connector Pin Diagram by Ryan M


EEC IV Connector Pin LEGEND Bronco & Ford Truck & Van: 4.9, 460, 5.0, 5.8;
Source: by Ryan M at Ford Fuel Injection
 

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FWC_Bronco

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Yo,
No, go to the EEC connector pin instead; test between EEC pin number 37 and VPWR pin at transmission vehicle harness connector.

Do same for EEC pin number 57 and VPWR pin at transmission vehicle harness connector.





EEC IV 60 Pin Connector Pin Diagram by Ryan M


EEC IV Connector Pin LEGEND Bronco & Ford Truck & Van: 4.9, 460, 5.0, 5.8;
Source: by Ryan M at Ford Fuel Injection
Interesting...

I followed the procedure and I am getting more than a .5 volt change when I cycle the throttle and probe the TCC output and VPWR. It would flash from 0 to 1.5 roughly. Does that eliminate a faulty pcm?

If it was a fault in the solenoid pack or TC internals I would think it would not work at all. It’s hooked up to a toggle switch and will work and hold overdrive when grounded.

Any ideas?
 
Last edited:

FWC_Bronco

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Yo,
Part 2.
Solved! Sort of...

I initially installed a toggle switch to rule out tc mechanical failure by "splicing" it in to the TCC output wire for convenience. I used a common on/off accessory switch (with indicator) and wired it backwards to created a switched grounding mechanism. I left it in place thinking it would not affect anything...

Once I verified the PCM was sending a signal to the harness I started thinking that having anything spliced into those wires might cause problems. So I removed the switch and reset the computer. OD is now working!

My 629 code is now gone and the truck is shifting much better. My only complaint is the brake switch will not disengage OD long enough for me to gain enough speed before locking again.

Maybe someone with more electrical expertise can explain this. My only thought is the toggle switch may have allowed some "bleed through" and was causing the PCM to sense a fault...
 
Last edited:

Skitter302

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I see some corrosion, but it doesn't look all that bad. Maybe you can see something that I don't. Check the following pics in my garage.
https://www.supermotors.net/registry/media/1157426
https://www.supermotors.net/registry/media/1157427
That part in your photo has some corrosion that shouldn't be there and it almost looks like something under it has gotten hot and warped, could just be the angle of the photo. Your photos remind me of my Failed PCM. My issue was that unplugging the EGR made 3rd gear performance better at part throttle. Photos included of my failed EEC for reference.

To fix my issue I took the opportunity to replace my SD EEC with a MAF EEC. That is an expensive route to go and not a financial commitment most are interested in taking on. I will say my Bco works amazing now.
 

FWC_Bronco

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Any idea what would cause the lockup to not disengage long enough to gain speed? If I tap the brake pedal it will unlock for just about a second and then drop back down.

I'll BOTL for another computer. Mine is a WAY1 and I can't find a reasonably priced replacement...
 

miesk5

96 Bronco 5.0
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Yo Al,
The brake on/off switch tells the powertrain control module when the brakes are applied. The switch is closed when the brakes are applied and open when they are released. The PCM uses this signal to disengage torque converter clutch when brake is applied.​
Symptoms: Failed on or not connected — Torque converter clutch will not engage at less than 1/3 throttle. Failed off — Torque converter clutch will not disengage when brake is applied.
Diagnostic Trouble Codes: 536
 

sinker4

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My 1995 had a similar issue. The OD light would flash and the trans would shift hard.After chasing my tail for years it turned out to be the P.S.O.M. [ programmable speedometer odometer modual ]on the back of the instrument cluster. I sent it to a speedometer shop in Fla.and they fixed it. Google PSOM
 

FWC_Bronco

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Yo FWC,
Any new codes?
Not yet. Transmission is shifting smooth and holding overdrive.

My main focus at the moment is getting the EGR functioning again.

I bypassed the vacuum solenoid to see if EGR valve would close, but the vacuum was too weak.

If I apply manifold vacuum directly to the EGR it will open and cause the truck to die. AC works at all speeds so I don't think there's an issue with the vresser.

I'll pull codes tonight and report back.

Thanks,
 

FWC_Bronco

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Yo FWC,
Any new codes?
I took the truck for a short trip about 1.5 hours away. About 30 min into the drive the truck felt like it was slipping into neutral and hunting for the right gear... The only way I made it home was by disabling overdrive.

I’ll pull codes but I’m hoping it’s electrical. Just driving around town it feels fine and this only occurred between 70-80mph.

Any thoughts?
 
Last edited:

miesk5

96 Bronco 5.0
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Yo Richard, hang in there and hope you can keep your Bronco somehow. I can't drive our 96 due to vision loss, but my much-better-half wheels it around with me as the passenger dummy.😎😎

I use an adjustable Drive model cane. Handle and length adjust and strap helps me not drop it. But I DO, A LOT!
Drug store prices are lower.

My biggest issue with each replacement was trying to walk upright, not like a cave man or monkey🐒

BALANCE EXERCISES are good. Began just standing still hold cane off floor for as long as possible, then up to a minute and twisting upper body over a bit in different directions.

Al
 

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