Here is your opportunity to demonstrate your prowess in technical knowledge and experience.

At 2PM today, Wednesday, I will be taking my car in to the shop for an analysis and resolution to the below problem. I will either have a fixed car, with problem resolved or ... an unfixed car without a resolution.

I do not know what the problem is, but below are the symptoms:

SES CODE: P1657 "1-4 Upshift Solenoid Control Circuit "

The car is a 1996 Z28/SS with a 6-speed.

HINT: The code will come back on within seconds after a DTC clear and engine restart. I removed my Skip-Shift Eliminator, but that did not satisfy the SES code from coming back on, so I put it back on and then cleared the codes, but it came back on within seconds.

 

isnt that an a4 code?

 

Well if it just throws a light and doesn't hurt anything i wouldn't spend the money to take it to a shop. Someone on here may know what it is alll about.

 

A short or open in your skip shift solenoid wire harness.

 

My list shows P1657 as "2nd and 3rd Gear Blockout Telay Cirucit Malfunction"..... in other words the skip shift solenoid. Code sets when the PCM engages the solenoid and it sees near +12V on the circuit when its commanded to engage (open circuit), or if it sees near "0" voltage in the circuit (short circuit) when the solenoid is "off". The test is peformed continuously, and takes 5 seconds.

 

Yeah, something isn't right with the skip shift wiring or even your simulator is bad.

 

UPDATE:

Scheduled service was delayed until today. Issue is NOT resolved. Voltage is present at solenoid/SS eliminator and on PCM. Installed temporary wire, bypassing existing circuitry, between PCM and Solenoid/SS eliminator. Error still returns after resets.

No fuse in circuit, only PCM and Solenoid and wiring??? Solenoid is essentially removed from problem, with SS eliminator. Wiring has been eliminated... PCM?

 

No fuse????? My book shows fuse 10(20 amp) underhood supplies current through connector C105(black 8 pin near the PCM) on the pink wire. If you have voltage all the way to the PCM then you have proved the fuse is good, wiring should be good and the solenoid has continuity.

You should try cycling the solenoid with a scanner to see(I should say hear) what is happening. Since you have voltage at the PCM with both the solenoid connected and the simulator. It appears the PCM has some sort of problem.

Remember the PCM has a driver circuit and a monitor(or fault detection) circuit of sorts. One of the 2 being faulty, will throw the code.

 

Problem Solved:

Okay, this required two mechanics (the first doing nothing remarkable), the second being the Chevrolet Dealer.

The problem (P1657) as noted above appeared to be confined to the PCM. In fact, it was the wiring. Apparently, the connector that plugs into the tranny solenoid (and skip-shift eliminator) had two defective connections. The tech snipped off the ends, and replaced the entire connector and that was it.


This was a very weird bug, because we tested for voltage and it was present. The Skip-Shift also worked normally when I drove it without the eliminator. But apparently, it was only working intermittently. As such, it was just enough of a flaky connection to cause the PCM to spit out a DTC, yet still work...

 

So what do I win???

 

I am proud to announce the winner of "Stump the Chump" contest: Z28SSOR in 1st place for his correct analysis . 2nd place goes to "Shoebox" for his correct analysis (but came in a little later) and "Honorable Mention" to Injuneer for his additional insight and correct analysis.

Thanks for all your help. We have some great technicians here!